Fix behavior of TRIM with computed trim characters

[mgill25]

Resolves #69922

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Function TRIM with computed empty trim characters are now correctly handled. Example: SELECT TRIM(LEADING concat('') FROM 'foo') (Issue #69922)

[robot-ch-test-poll4]

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[clickhouse-gh]

Workflow [PR], commit [19eef40]

[rschu1ze]

Stateless tests (azure, asan, 1/3):

• 02421_truncate_isolation_no_merges: 02421_truncate_isolation_no_merges is flaky #75981

Integration tests (release, 4/4):

• test_dns_cache: Integration test test_dns_cache is flaky #75982