Converge the SourceBrowser subtree: normalize EOL/BOM, unify package management, drop dead code

[tannergooding]

Reduces the divergence between the vendored src/SourceBrowser/ subtree and the standalone SourceBrowser so future porting/back-porting between them is trivial. No runtime behavior changes for indexing or serving; the subtree still builds and all tests pass (184 HtmlGenerator + 40 SourceIndexServer + 10 BinLogToSln).

The changes are split into focused commits so the large mechanical normalization can be reviewed (or skipped) independently of the real edits.

Normalize line endings and BOMs

Adopts a .gitattributes matching the standalone repo (* text=auto, *.cmd eol=crlf, binary rules for png/ico/dll/snk) and renormalizes every text file to check-in LF / check-out native, no BOM. This is the bulk of the diff and is purely mechanical -- review with whitespace/EOL ignored.

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Converge package management

• Adds a subtree-root Directory.Packages.props so the sibling TestCode/ fixtures fall under central package management, matching the main projects.
• Moves NuGetVersion into Directory.Build.props instead of hardcoding it per-project.
• Drops the redundant per-reference MSBuild versions (now supplied centrally) and prunes unused PackageReferences from MEF and GitGlyph.
• Targets the TestCode test fixtures at net10.0.

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Drop dead code

• Removes the unused Log.WaitForCompletion/OnCompleted plumbing -- the flush-before-exit guarantee still lives in Log.Close() (CompleteAdding + Join), which is unchanged and called at every exit path.
• Removes the no-op [HandleProcessCorruptedStateExceptions] (ignored on modern .NET) and unused using directives.

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Quiet the default indexing run

• Gates the assembly-load and MSBuild-toolset dumps in HtmlGenerator behind SOURCEBROWSER_ASSEMBLY_DIAGNOSTICS=1 so normal runs stay quiet, keeping the diagnostics available on demand.

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Remove dead config

• Removes GitGlyph/app.config; GitGlyph targets net10.0 and never references it, and its assembly binding redirects are ignored on modern .NET.

[tannergooding]

This is best reviewed with whitespace ignored. There was a lot of bad line-endings (not matching standard convention of check-in unix style, check-out host format) that were making diffs and ensuring source-indexer and sourcebrowser were in sync complex.

The actual changes, ignoring the whitespace/bom, is small and trivial.

[jeffhandley]

I reviewed commit-by-commit, which made this approachable. Looks nice and clean and this is a good modernization of the codebase.

[tannergooding]

Thanks. This should make it massively simpler to mirror things between now as well.