Shard output of cpp transpiler.

Large designs can lead to huge, slow-to-build c++ sources. This change produces one file per type.

PiperOrigin-RevId: 870023245

Automated Code Change

PiperOrigin-RevId: 869528602

Merge pull request #3774 from google:dependabot/bazel/bazel_features-…

Automated Code Change

PiperOrigin-RevId: 868470196

Migrate xls::down_cast to use absl::down_cast.

The xls::down_cast functions are now implemented as direct calls to absl::down_cast and are marked with ABSL_DEPRECATE_AND_INLINE.

Note that we also bump our abseil dep to grab a newer version with absl::down_cast.

PiperOrigin-RevId: 866676858

Update more tests in proc lowering block eval PSC test to work.

PiperOrigin-RevId: 866099089

Integrate LLVM at llvm/llvm-project@b4b8d4e5d062

Updates LLVM usage to match
[b4b8d4e5d062](https://github.com/llvm/llvm-project/commit/b4b8d4e5d062)

PiperOrigin-RevId: 865658424

Ensure aot-compiler works with targets where proc/function and block …

Fix Codegen() in v1.5 to return the pipeline metrics and residual data.

This gets codegen_main_test to pass against 1.5 aside from the necessary golden file changes.

PiperOrigin-RevId: 864582524

Don't lower an unscheduled proc to a block in codegen 1.5 when pipeli…