[Codegen] Add PipelineAttrInterface and PassPipelineAttr (#23590)

This change adds an attribute interface for representing pass pipelines
and a single basic attribute that uses the string based pass interpreter
to populate a pipeline. The intent of this change is NOT to induce a
refactor of all the pass pipelines, instead it's primarily to make
testing structural pipeline changes with partially lowered inputs much
easier. Today if you want to work on a change that affects later stages
of a pass pipeline but will also require changes to earlier steps, it's
hard to stage those changes since there isn't a convenient way to jump
into the middle of a codegen pass pipeline (unlike the rest of the
compiler which offers distinct stages).

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>