Support parsing Oracle RMAN CHANGE DB_UNIQUE_NAME SQL

[terrymanu]

• Add the CHANGE DB_UNIQUE_NAME FROM identifier TO identifier branch to the Oracle DAL change rule introduced for RMAN CHANGE statements, covering the rename form requested by issue Support parsing Oracle CHANGE DB_UNIQUE_NAME sql #27017
• Reuse the field-less OracleChangeStatement passthrough model and existing CHANGE visitor rule, so no statement, visitor or assert change is required
• Add the CHANGE DB_UNIQUE_NAME FROM BOSTON_A TO BOSTON_B parser IT case

Fixes #27017

[terrymanu]

Result

Review Result: Mergeable

This PR fills the only remaining syntax gap of issue #27017 in the smallest correct way: it adds CHANGE DB_UNIQUE_NAME FROM identifier TO identifier to the Oracle DAL change rule, fully reusing the field-less passthrough model established by #39581, with a regression parser IT case. No blocking issue was found.

Evidence

• Scope verification: PR head 8b80a8e2db3 (1 commit, 3 files, +4/-1), base cfa4dfe7b50. Local HEAD equals the public head and the local triple-dot file list matches the authoritative GitHub list 3/3 (verified by the inventory script).
• Official syntax evidence: the Oracle 21c RMAN Reference CHANGE page (docs.oracle.com/en/database/oracle/oracle-database/21/rcmrf/CHANGE.html) defines CHANGE DB_UNIQUE_NAME FROM db_unique_name TO db_unique_name; and the PR case BOSTON_A → BOSTON_B matches that documentation and the issue sample. Supporting RMAN commands as Oracle DAL statements is established precedent (Support parsing Oracle SET DBID sql #39554 SET DBID/LIST/REPORT, Support parsing Oracle RMAN CHANGE SQL #39581 CHANGE family).
• Grammar correctness: the new alternative at parser/sql/engine/dialect/oracle/src/main/antlr4/imports/oracle/DALStatement.g4:207 is added as the first alternative; its leading token DB_UNIQUE_NAME is disjoint from the four existing alternatives (BACKUPSET/DATAFILECOPY/COPY/BACKUP), so no shadowing or path change occurs. CHANGE CATEGORY inside alterOutline uses a different entry token and is unaffected. changeOption is intentionally not attached to this form, matching the official syntax. The value position uses identifier, same as the merged forDbUniqueName : FOR DB_UNIQUE_NAME identifier precedent (Support parsing Oracle SET DBID sql #39554).
• Reuse and blast radius: the dispatch (OracleStatement.g4:169 | change), visitChange, the field-less OracleChangeStatement, and the assert/JAXB registration all pre-exist from Support parsing Oracle RMAN CHANGE SQL #39581 and are unchanged in this PR, keeping the model consistent. Oracle is a trunk dialect with no branch dialects, so no diff markers are required; ANTLR generated artifacts are untracked build output with no baseline impact.
• Test validity: the new change_db_unique_name_oracle case in sql/supported/dal/change.xml and case/dal/change.xml has a unique id and its expected shape matches the 8 existing change cases; removing the grammar branch would fail this case, which provides real regression protection.
• Local verification (sanitized): ./mvnw -pl test/it/parser -am -DskipITs -Dspotless.skip=true -Dtest=...oracle.InternalOracleParserIT ... test → Tests run: 1940, Failures: 0, exit code 0; ./mvnw spotless:apply -Pcheck -T1C and ./mvnw checkstyle:check -Pcheck -T1C both BUILD SUCCESS (exit code 0). The verified content is byte-identical to commit 8b80a8e2db3.

Coverage

• Reviewed head: 8b80a8e2db3; requirements: PR description plus Fixes #27017.
• Files: 3/3 accounted for (behavior clusters: oracle-change-grammar 1 file, oracle-change-it-case 2 files), no churn-only files; all three discovery lenses (root cause/behavior, blast radius/contracts, tests/runtime) completed, convergence pass found zero new candidates; no candidate passed the Finding Proof Gate as a blocker.
• Dialect: Oracle (trunk dialect, no branch dialects); no shared code or other dialect touched. Official docs: Oracle 21c RMAN CHANGE page. Repository docs/baselines: no change required.
• Scope notes: the remaining CHECK/CASE WHEN snippets in issue Support parsing Oracle CHANGE DB_UNIQUE_NAME sql #27017 are expressions rather than statements, hence outside statement-parsing scope and not a PR gap; unrelated local uncommitted worktree changes (oracle select-special-function.xml) are not part of the PR head and were excluded from review scope.
• Gaps: none. CI not reviewed (this result is code-scope only; GitHub Actions/checks were neither queried nor judged).