sql/schemachanger: ALTER COLUMN TYPE not supported for columns in inverted indexes

ALTER COLUMN TYPE that requires a rewrite of the on-disk data is not yet
supported when the column is part of an inverted index.

This is split out from cockroachdb/cockroach#47636, which tracked ALTER COLUMN
TYPE for columns that are part of an index. Support for non-inverted secondary
index columns has landed in the declarative schema changer; inverted indexes
remain unsupported because their special encoding is not yet handled by the
index-rebuild path used for the column swap.

Attempting it currently returns:

ALTER COLUMN TYPE requiring rewrite of on-disk data is currently not
supported for columns that are part of an inverted index

Code reference:
- [pkg/sql/schemachanger/scbuild/internal/scbuildstmt/alter_table_alter_column_type.go](https://github.com/cockroachdb/cockroach/blob/master/pkg/sql/schemachanger/scbuild/internal/scbuildstmt/alter_table_alter_column_type.go)

Epic CRDB-44826

Jira issue: CRDB-65861

Start in pkg/sql/schemachanger/scbuild/internal/scbuildstmt/alter_table_alter_column_type.go and trace the index-rebuild path used for the column swap. Reproduce ALTER COLUMN TYPE on a column in an inverted index, then follow the existing handling for supported index columns. Done means the on-disk rewrite succeeds for inverted-index columns instead of returning the current unsupported error.

Written by the indexing model from the issue text.