Add ability to undelete a column

[fbertsch]

• Extract the latest instance of that column name from historical schemas
• Required columns will be come non-required
• The parent field must already be present in the schema
• Add spark procedure call to run undelete

[fbertsch]

@bryanck - could you take a look?

This API is imperfect, since it doesn't allow an undelete of a field that has been recreated, i.e.:

1. ALTER TABLE ADD COLUMN x string
2. ALTER TABLE DROP COLUMN x
3. ALTER TABLE ADD COLUMN x int
4. ALTER TABLE DROP COLUMN x
5. CALL system.undelete_column('my.iceberg_table', 'x')

The string version of x is unrecoverable. I doubt this is such a large use case. To support that, we'd need an API to expose the historical fields of a table, and then undelete by ID, which is probably too much complexity for a good API.

[fbertsch]

Fixes #14488

[fbertsch]

This generated yaml changed the structure - I can try to move it back around to minimize this diff

[steveloughran]

test coverage looks good. the only corner case I could add would be

• add and delete a column count twice (so having different ids)
• verify the undeleted column is the most recent one.

would be a simple addition to testUndeletePreservesFieldId

[fbertsch]

Added, thank you!

[steveloughran]

thanks. new test looks good; ensures that scan happens in the correct order. You'll need actual iceberg committers to review and approve the rest of the patch now...