starknet_transaction_prover: capture prover panics through the observability hook

[avi-starkware]

Summary

Capture prover panics through the service's existing observability hook. This is the first half of the unsupported-mod-builtin work; it does not classify builtins or introduce a new RPC error code.

• Record panic locations on the panicking thread while preserving structured logging, payload redaction, and backtraces.
• Catch unwinds at the synchronous prover boundary and return ProverPanic with the message and available location.
• Clear recorded locations before and after each call to avoid stale attribution.
• Keep panics and returned prover errors mapped to JSON-RPC -32603. The spec pin is unchanged.
• Test payload forms, exact locations, stale and nested captures, logging, and RPC mapping.

Stacked on #15124. #15131 adds unsupported-builtin classification, spec error 1002, and real-proving regressions.

Verification

Run independently on this layer, using its own pinned spec:

• Proving-enabled library suite: 148 passed, 6 ignored.
• Non-proving library suite: 140 passed, 5 ignored; one doc test passed.
• Clippy with -D warnings passed in both configurations. Formatting passed.

cargo +nightly-2026-01-15 test --locked -p starknet_transaction_prover --features stwo_proving --release --lib --quiet
cargo +nightly-2026-01-15 clippy --locked --release -p starknet_transaction_prover --features stwo_proving --all-targets -- -D warnings
cargo test --locked -p starknet_transaction_prover --quiet
cargo clippy --locked -p starknet_transaction_prover --all-targets -- -D warnings

[reviewable-StarkWare]

This change is