Integrate LLVM at llvm/llvm-project@52ed6791f87a

Updates LLVM usage to match
[52ed6791f87a](https://github.com/llvm/llvm-project/commit/52ed6791f87a)

PiperOrigin-RevId: 759414853

Move state-channel conversion logic into `passes_ng` and turn it into…

This change generalizes the analysis within the resource sharing pass…

Add a design doc for a new approach to allowing multiple ops per channel

PiperOrigin-RevId: 757957057

Integrate LLVM at llvm/llvm-project@2d287f51eff2

Updates LLVM usage to match
[2d287f51eff2](https://github.com/llvm/llvm-project/commit/2d287f51eff2)

PiperOrigin-RevId: 756508479

Improve const-ness of module in run routines, and some of its methods.

PiperOrigin-RevId: 756032997

Automated rollback of commit 97a4b6efdb652a9ae06092712a9a785558a49f40.

PiperOrigin-RevId: 755680460

Improve metrics reporting of the optimization pipeline.

This includes a number of fixes/changes:
* Gather metrics in un-aggregated form, one proto for each time a pass is run. The data is organized hierarchically mirroring the hiearchical structure of the pass pipeline.
* Add a utility which dumps a table from the proto metrics data. The utility produces two tables: one aggregated by pass name, and one hierarchically organized.
* Fix bug where the invariant checkers were not being run for some passes, specifically those within CapOptLevel or IfOptLevelAtLeast compound passes. As part of this fix clean up the pass_base code a bit. Make RunNested a method on PassBase which makes CompoundPassBase and PassBase a bit more interchangeable.
* Add numerous test for various bits of PassBase functionality which were previously untested.

PiperOrigin-RevId: 755096116

[XLS] Simplify apfloat using abs_diff

APFloat previously used a custom sign-magnitude difference function; this is now redundant with the new absolute difference library, so we switch to use that instead.

To enable this, we also add `abs_diff` to the list of built-in libraries, so it will be imported from the DSLX stdlib location.

PiperOrigin-RevId: 754159246

Refactored block_conversion and added accessor functions for proc-scoped

channels to nodes.

PiperOrigin-RevId: 753768577