[UTC] Add fallback support for specific metadata, and check their defs

This prevents update_cc_tests.py from emitting hard-coded identifiers
for metadata (global variable checkers still check hard-coded
identifiers). Instead it emits regex checkers that match even if the
identifiers change. Also adds a new mode for --check-globals: instead of
simply being on or off, it now has the options 'none', 'smart' and
'all', with 'none' and 'all' corresponding to the previous modes.

The 'smart' mode only emits checks for global definitions referenced
in the IR or other metadata that itself has a definition checker
emitted, making the rule transitive. It does not emit checks for
attribute sets, since that is better checked by --check-attributes. This
mode is made the new default. To make the change in default mode
backwards compatible a version bump is introduced (to v3), and the
default remains 'none' in v1 & v2.

This will result in metadata checks being emitted more often, so filters
are added to not check absolute file paths and compiler version git
hashes.

rdar://105239218

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