Summary:
Depends on D4868. This is part of a series of changes to make the way the compiler handles metadata work a bit more easily with agent metadata pruning.
The new flow will remove the _attr columns created by maps, and MetadataIRs will now be considered intermediate nodes that are compiled to a func that generates them.

New analyzer flow:
1. MetadataIR has its MetadataProperty set in ResolveMetadataPropertyRule
2. MetadataIR is converted to the func that creates it (upid_to_pod_name(upid) for example) in ConvertMetadataRule. ConvertMetadataRule also sets the metadata_type annotation on the output func.
3. PropagateExpressionAnnotationsRule (D4868) will propagate the metadata_type annotation in the generated func to all of the places that generated func is renamed or set to
a column. for example, if that func is used to produce a column, which is then renamed and used as a group by column, the annotations will follow it as long as the column is intact.

Then, consumers of the IR that need to know about metadata type of an expression (such as metadata agent pruning) only have to look at the metadata type annotation. This avoids the problem
of those consumers needing to check for the various cases that exist today.

Test Plan: added

Reviewers: philkuz, jamesbartlett, zasgar, #engineering

Reviewed By: philkuz, #engineering

JIRA Issues: PP-1928

Differential Revision: https://phab.corp.pixielabs.ai/D4877

GitOrigin-RevId: 67e5ca2faa13e816b39f18d668e9cbd1766d893a