[SPARK-57054][SQL] Make view collation sticky across ALTER SCHEMA DEFAULT COLLATION

[ilicmarkodb]

What changes were proposed in this pull request?

Remove the AlterViewAs rewrite case from ApplyDefaultCollation.resolveDefaultCollation. It used to fold the namespace's current default collation into a view whose persisted PROP_COLLATION was empty, on every ALTER VIEW AS.

Why are the changes needed?

A view's collation should be fixed at creation time. The removed rewrite let a later ALTER SCHEMA ... DEFAULT COLLATION retroactively change an existing view's literal types on the next ALTER VIEW AS:

CREATE SCHEMA s;
CREATE VIEW v AS SELECT 'a' AS c1;            -- UTF8_BINARY
ALTER SCHEMA s DEFAULT COLLATION UTF8_LCASE;
ALTER VIEW v AS SELECT 'x' AS c1;             -- was: UTF8_LCASE; now: UTF8_BINARY

Does this PR introduce any user-facing change?

Yes. ALTER VIEW AS no longer picks up the namespace's current default collation for a view that was created without one — the view's collation stays sticky from creation.

How was this patch tested?

Updated the existing V1 and V2 tests to assert the new sticky behavior.

Was this patch authored or co-authored using generative AI tooling?

No.