Add the initial inlining infrastructure.

This defines a set of initial utilities for inlining a region(or a FuncOp), and defines a simple inliner pass for testing purposes.
A new dialect interface is defined, DialectInlinerInterface, that allows for dialects to override hooks controlling inlining legality. The interface currently provides the following hooks, but these are just premilinary and should be changed/added to/modified as necessary:

* isLegalToInline
  - Determine if a region can be inlined into one of this dialect, *or* if an operation of this dialect can be inlined into a given region.

* shouldAnalyzeRecursively
  - Determine if an operation with regions should be analyzed recursively for legality. This allows for child operations to be closed off from the legality checks for operations like lambdas.

* handleTerminator
  - Process a terminator that has been inlined.

This cl adds support for inlining StandardOps, but other dialects will be added in followups as necessary.

PiperOrigin-RevId: 267426759