feat: reuse typed prepared plans and reduce execution overhead

[KKould]

What problem does this PR solve?

The old prepare path cached only a parsed SQL Statement: each execution still bound and optimized the query. Parameterized INSERT ... VALUES was also limited by bind-time constant evaluation. This PR makes prepared execution reuse a typed plan and updates the dependent execution paths.

Issue link: N/A

What is changed and how it works?

1. Prepare and reuse plans (d9e8766): Database::prepare / DBTransaction::prepare take SQL plus positional parameter types and produce a PreparedPlan containing a bound, optimized plan and its arena. execute supplies values, clones the logical plan, and runs it without repeating parsing/binding/optimization. Placeholders are typed $1, $2, etc.; selected index ranges are bound and, when possible, specialized from residual predicates for the current parameter values.
2. Rework INSERT / VALUES (d9e8766): retain row expressions as ExprRef in ValuesOperator instead of requiring bind-time constants. Resolve explicit DEFAULT while binding; evaluate and cast VALUES expressions per execution, then apply missing-column defaults and target-column length/nullability checks in Insert. This enables expressions and positional parameters in prepared INSERT ... VALUES, as well as expression-based standalone VALUES.
3. Bind parameters per execution (db7d064): add ParamArena over the immutable prepared PlanArena, copying and replacing only parameter-dependent expressions; propagate MetaArena through the execution path so repeated executions do not mutate the cached plan. Index lookups are bound on the execution-local plan.
4. Reduce execution and index-key overhead (45e3b79): keep ExecNodes in place instead of moving them out of the arena on every next_tuple; use arena-backed rewrite for projection/index expressions. Simplify DataValue::Tuple while deriving lower/upper prefix-bound semantics from range context during comparison and index-key encoding; restore tuple-buffer reuse in SeqScan and IndexScan.
5. Update consumers and coverage: TPCC backends now cache PreparedPlans with explicit parameter/result types and positional values; SQLite adapts to the shared parameter IDs. Add prepared-plan/index-range unit tests and SQL logic cases for VALUES, INSERT, grouping and indexed predicates.

Code changes

• Has Rust code change
• Has CI related scripts change

Check List

Tests

• Unit test — cargo test --lib --features decimal (426 passed)
• Integration test — ran values.slt, group_by.slt, where_by_index.slt, where_by_index_explain.slt through sqllogictest-test
• Manual test
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility — public binder::prepare / db::prepare (AST preparation) and Database::execute / DBTransaction::execute signatures change to the typed PreparedPlan API.

Note for reviewer

cargo fmt --all -- --check passes. The four-variant 720-second TPCC results are recorded in tpcc/README.md; this run used --cool-temp-c 75 because the machine idled above the runner's default 65°C gate.

Performance follow-ups (not addressed here):

• Recursive ScalarExpression::eval creates temporary DataValues and evaluates binary/cast nodes one at a time. A no-table prepared arithmetic microbenchmark shows nontrivial per-expression execution cost; benchmark a specialized/compiled evaluation path separately.
• ParamArena::new traverses the entire prepared expression arena on every execution, even if only a few expressions depend on parameters. Investigate caching parameter-dependent expression references to avoid this scan.

Redundant casts/projections are not optimized by this PR.

[codecov]

Codecov Report

❌ Patch coverage is 94.02368% with 217 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.09%. Comparing base (357cde1) to head (488c19d).

Files with missing lines	Patch %	Lines
src/expression/range_detacher.rs	90.43%	55 Missing ⚠️
src/planner/arena.rs	74.86%	45 Missing ⚠️
src/types/value.rs	87.50%	17 Missing ⚠️
src/db/prepared.rs	96.32%	16 Missing ⚠️
src/expression/evaluator.rs	91.97%	13 Missing ⚠️
src/expression/simplify.rs	83.67%	8 Missing ⚠️
.../optimizer/rule/normalization/combine_operators.rs	90.00%	8 Missing ⚠️
src/binder/parser.rs	95.28%	5 Missing ⚠️
src/function/lower.rs	58.33%	5 Missing ⚠️
src/function/upper.rs	58.33%	5 Missing ⚠️
... and 16 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #383      +/-   ##
==========================================
- Coverage   93.18%   93.09%   -0.09%     
==========================================
  Files         257      258       +1     
  Lines       45852    47487    +1635     
==========================================
+ Hits        42727    44209    +1482     
- Misses       3125     3278     +153     

Flag	Coverage Δ
rust	93.09% <94.02%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/binder/aggregate.rs	97.68% <100.00%> (ø)
src/binder/alter_table.rs	100.00% <ø> (ø)
src/binder/analyze.rs	96.00% <ø> (ø)
src/binder/copy.rs	71.73% <ø> (ø)
src/binder/create_index.rs	90.47% <ø> (ø)
src/binder/create_table.rs	87.67% <ø> (ø)
src/binder/create_view.rs	100.00% <ø> (ø)
src/binder/delete.rs	100.00% <ø> (ø)
src/binder/describe.rs	100.00% <ø> (ø)
src/binder/distinct.rs	98.50% <100.00%> (ø)
... and 157 more

... and 2 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.