[xls] Add `QueryEngine::Covers`

This makes it simpler to test whether a node can equal a concrete `Bits` value.

PiperOrigin-RevId: 780656513

Automated rollback of commit de1f57d2d9254fb722d11a8232212ecf03bec00e.

PiperOrigin-RevId: 780345867

Integrate LLVM at llvm/llvm-project@696c0f92e0fe

Updates LLVM usage to match
[696c0f92e0fe](https://github.com/llvm/llvm-project/commit/696c0f92e0fe)

PiperOrigin-RevId: 778888035

Add a new tool to show the relation of pipeline stages, channels and …

Avoid creating extra select/continuation values on pop context

after conditions are applied mid-context.

PiperOrigin-RevId: 777696517

Add documentation about how to run mdformat.

PiperOrigin-RevId: 776790558

Integrate LLVM at llvm/llvm-project@bae48ac3c0e6

Updates LLVM usage to match
[bae48ac3c0e6](https://github.com/llvm/llvm-project/commit/bae48ac3c0e6)

PiperOrigin-RevId: 775879001

Add a couple of utilities for manipulation of instantiations.

This makes creating and removing instantiations less error prone.

PiperOrigin-RevId: 775504376

Enable TIv2 for `some_caps_streaming` example.

https://github.com/google/xls/issues/2419

PiperOrigin-RevId: 774974588

Fixed bug where channel array (with size being an expression) fails t…