fix: accept LargeUtf8 and Utf8View patterns in SIMILAR TO planning

[u70b3]

Which issue does this PR close?

• Closes SIMILAR TO: SQL planner rejects non-literal LargeUtf8 / Utf8View patterns #23732

Rationale for this change

Follow-up to #23704, which made the TypeCoercion analyzer coerce SIMILAR TO operands to a common string type. The SQL planner still rejects LargeUtf8 and Utf8View patterns before the analyzer ever runs:

SELECT s FROM test, patterns WHERE s SIMILAR TO arrow_cast(pat, 'Utf8View');
-- error: Invalid pattern in SIMILAR TO expression

Now that the analyzer coerces both operands, this planner restriction is unnecessary (and inconsistent with LIKE, whose planner path has no such check).

What changes are included in this PR?

• datafusion/sql/src/expr/mod.rs: the pattern-type check in sql_similarto_to_expr now accepts Utf8 / LargeUtf8 / Utf8View / Null instead of only Utf8 / Null.
• datafusion/sqllogictest/test_files/type_coercion.slt: regression tests with non-literal Utf8View and LargeUtf8 patterns (plus a NOT SIMILAR TO case), next to the existing SIMILAR TO panics ('failed to downcast array') when operand types differ (e.g. NULL pattern, Utf8View vs Utf8) #22886 regression tests.

The planner relaxation and tests were originally part of #22887; this PR lands the remaining piece of it.

Are these changes tested?

Yes — new sqllogictest cases in type_coercion.slt. The existing planner rejection of non-string patterns (SELECT 'a' SIMILAR TO 1) still errors as before.

Are there any user-facing changes?

Yes: SIMILAR TO queries with non-literal LargeUtf8 / Utf8View patterns that previously failed during SQL planning with Invalid pattern in SIMILAR TO expression now plan and execute successfully. No breaking API changes.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.71%. Comparing base (050046a) to head (7738741).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #23735      +/-   ##
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- Coverage   80.71%   80.71%   -0.01%     
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  Files        1089     1089              
  Lines      368750   368751       +1     
  Branches   368750   368751       +1     
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- Hits       297631   297627       -4     
- Misses      53375    53376       +1     
- Partials    17744    17748       +4     

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[adriangb]

Can we add tests for teh null case?

[u70b3]

Done in add3f8d — added a literal NULL pattern in the table context and a non-scalar Null-typed pattern column (CREATE TABLE pn AS SELECT NULL AS pat), both evaluate to NULL.