Integrate LLVM at llvm/llvm-project@06ae0c2a1086

Updates LLVM usage to match
[06ae0c2a1086](https://github.com/llvm/llvm-project/commit/06ae0c2a1086)

PiperOrigin-RevId: 784770381

Improve UnionQueryEngine::Of to take unique_ptr<QueryEngine>s and Que…

Fixed a PrioritySelect bug in verify_node.cc involving a wrongly type…

Automated Code Change

PiperOrigin-RevId: 782721801

Integrate LLVM at llvm/llvm-project@f8cb7987c64d

Updates LLVM usage to match
[f8cb7987c64d](https://github.com/llvm/llvm-project/commit/f8cb7987c64d)

PiperOrigin-RevId: 782220044

Control opt pipeline using toolchains.

Toolchains allow one to configure aspects of compilation in a reasonably straightforward way. This change makes a toolchain responsible for selecting the default pass pipeline used by XLS.

Note that this does not currently allow toolchains to control the actual tools used in compilation and the separate (confusingly named) xls_toolchain remains the only way to do that and is unchanged.

PiperOrigin-RevId: 781840644

Added 31 similar IR nodes to the IR Fuzzer.

I added more IR nodes, specifically IR ops similar to Add because we already have infrastructure to easily add these nodes. This required updating the proto, visitor, and IR node generator. A lot of testing and debugging was done to iron out test cases associated with different ops. This CL is large because most of the code dealing with Ops is repetative and configuring large protobuf tests.

PiperOrigin-RevId: 781251643

[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