Integrate incremental generator fixes and restore BITSKIT003

[RejectKid]

Summary

• merge upstream PR #5 with its original commit history and contributor attribution intact
• make the source generator genuinely incremental by removing retained Roslyn symbols, syntax nodes, mutable lists, and CompilationProvider
• move generator diagnostics into analyzers
• restore BITSKIT003 for supported memory-backed bit fields that omit their required FieldType
• prevent invalid generated properties after analyzer errors
• add incremental caching and BITSKIT003 regression coverage
• keep the analyzer package self-contained by avoiding the upstream PR's unbundled Microsoft.Bcl.HashCode runtime dependency
• remove the dependency-review workflow because GitHub's dependency-review API rejects fork repositories

Why

The generator previously re-ran for insignificant compilation changes and retained compiler objects in its incremental pipeline, which can cause IDE performance and memory problems. Upstream PR #5 fixes that architecture but intentionally omitted BITSKIT003; this integration restores the diagnostic without reintroducing non-incremental state.

Validation

• locked restore succeeds
• Release build succeeds with 0 warnings and 0 errors
• 4,557 tests pass on .NET 8
• 4,557 tests pass on .NET 10
• NuGet and symbol packages build and pass package-content validation
• generator assembly references only framework and Roslyn assemblies
• GitHub workflows pass actionlint

Attribution

The upstream incremental-generator work remains authored by ZingBallyhoo through the preserved merge history.