[fix](fe) Reject static partition assignments for OLAP tables (#70287)

Doris accepts both partition-name lists and static partition assignments
in INSERT statements. Static assignments such as
`PARTITION(dt='2026-11-04')` are supported by external-table write
paths; OLAP tables use partition names, or `PARTITION(*)` for automatic
overwrite partition detection.

### What problem does this PR solve?

Issue Number: None
Related PR: #58396 (introduced static partition overwrite syntax)
PR Type: Bugfix

Problem Summary:

An INSERT OVERWRITE on an OLAP table accepts
`PARTITION(dt='2026-11-04')` but silently discards the static partition
assignments when creating the table sink. The resulting empty
partition-name list is treated as a whole-table overwrite, so data in
unrelated partitions is removed. Reject static partition assignments
before constructing an OLAP sink, for both INSERT INTO and INSERT
OVERWRITE, including remote Doris targets. The error directs users to
partition names or automatic overwrite partition detection.

### Details

- **Frequency:** Reproducible whenever an OLAP INSERT OVERWRITE
specifies static partition assignments; ordinary INSERT INTO silently
ignores the same assignments.
- **Root cause:** The parser preserves assignments separately from
partition names, but both OLAP sink creation entry points ignore the
assignments.
- **Why existing tests missed it:** Parser tests verify that assignments
are accepted, and external-table tests exercise supported static
partition writes. They do not check that OLAP targets reject the
unsupported syntax or preserve unrelated partitions.
- **Fix:** Share an admission check between both OLAP sink creation
entry points and raise an analysis error before any write or partition
replacement.
- **Other paths and branches:** External connector sinks retain their
static partition assignments. Partition-name inserts, partition-name
overwrites, automatic partition detection, and explicit whole-table
overwrites retain their behavior.