Add optimize_manifests table procedure to Iceberg

[ebyhr]

Description

Add a new procedure that rewrites manifest files like rewrite_manifests in Spark.

ALTER TABLE {table} EXECUTE optimize_manifests;

Fixes #14821

Release notes

## Iceberg
* Add `optimize_manifests` table procedure. ({issue}`14821`)

[martint]

What does the function do? "rewrite manifests" is too vague, IMO, and doesn't convey what its purpose is. Why would one want to rewrite manifests? In what way are they rewritten?

[ebyhr]

@martint This is "compaction" about manifest files, e.g. merging 10 manifest files into one. Too many manifest files increase planning time because we must open each file.

[martint]

In that case, I would rename the function to either "compact_manifests" (if we think that's the only thing the function will do going forward), or "optimize_manifests".

[ebyhr]

Let me adopt "optimize_manifests".