[BugFix] Fix num_short_key_columns mismatch in partial tablet schema (backport #70586)

[mergify]

Why I'm doing:

Fix BE DCHECK crash num_short_keys <= sort_key_idxes.size() in SeekTuple::short_key_encode during column-mode partial update on primary key tables with separate sort keys (e.g. ORDER BY(k3, k2)).

TabletSchema::create copies num_short_key_columns from the source schema (e.g. 2), but sort_key_idxes in the partial schema may be empty when sort key columns are not in the partial column set. _init_from_pb then falls back to using key columns as sort keys (e.g. size=1), creating an inconsistency: num_short_key_columns(2) > sort_key_idxes.size()(1).

What I'm doing:

After constructing the partial tablet schema, ensure num_short_key_columns <= sort_key_idxes.size() to keep them consistent.

Trigger SQL:

CREATE TABLE tab1 (k0 int NOT NULL, k1 int, k2 int, k3 int, k4 int, k5 int, v1 int, v2 int)
PRIMARY KEY(k0) DISTRIBUTED BY HASH(k0) BUCKETS 1 ORDER BY(k3, k2)
PROPERTIES ("replication_num" = "1");

INSERT INTO tab1 VALUES (1,1,1,1,1,1,1,1);
SET partial_update_mode = 'column';
UPDATE tab1 SET k4 = 1;  -- crashes in ASAN build

Fixes https://github.com/StarRocks/StarRocksTest/issues/11136

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This PR needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport PR

Bugfix cherry-pick branch check:

• I have checked the version labels which the PR will be auto-backported to the target branch
  • 4.0
  • 3.5
  • 3.4

    ---

    This is an automatic backport of pull request [BugFix] Fix num_short_key_columns mismatch in partial tablet schema #70586 done by Mergify.