feat: parse UPDATE OR conflict algorithms in the SQLite dialect - #2885

Part of #2852 (the UPDATE OR part; WITHOUT ROWID and STRICT are not in this PR).

INSERT OR REPLACE already parsed, and #2853 added INSERT OR ABORT, FAIL, IGNORE and ROLLBACK. SQLite takes the same five conflict algorithms after UPDATE OR (lang_update), and the issue's table shows UPDATE OR IGNORE t SET a = 1 and UPDATE OR REPLACE t SET a = 1 stopping at Encountered: <K_UPDATE> / "UPDATE".

What changes:

• New enum UpdateConflictAlgorithm (ABORT, FAIL, IGNORE, REPLACE, ROLLBACK), next to UpdateModifierPriority.
• Update gets getConflictAlgorithm(), setConflictAlgorithm() and withConflictAlgorithm(). The value is null for an UPDATE without OR, so existing statements build the same object. Update.toString() and UpdateDeParser print OR <algorithm> right after UPDATE.
• The Update production reads [ <K_OR> RelObjectName() ] after UPDATE, and AbstractJSqlParser.updateOrAlgorithm maps the word to the enum. This is the shape feat: parse INSERT OR ABORT, FAIL, IGNORE and ROLLBACK (SQLite) #2853 settled on for INSERT OR, which keeps the addition to CCJSqlParser to one optional (the constant-pool headroom of JaCoCo instrumentation of CCJSqlParser is approaching the constant-pool limit #2866).
• UPDATE OR needs Dialect.SQLITE. Without it, or with a word that is not one of the five, the statement is a parse error.
• usage.rst lists UPDATE OR in the SQLITE row of the dialect table.

Tests, all in SQLiteTest:

• testUpdateOrConflictAlgorithm, one case per algorithm: parse and round trip through toString() and the deparser, in upper and lower case, and getConflictAlgorithm() returns that algorithm.
• testUpdateOrConflictAlgorithmNeedsSqliteDialect, one case per algorithm: rejected without the dialect.
• testUpdateOrUnknownAlgorithm: UPDATE OR NOTHING is rejected with the dialect.
• testUpdateWithoutConflictAlgorithm: a plain UPDATE keeps getConflictAlgorithm() null.

The two rejection tests would also pass on a parser with no UPDATE OR support at all; a comment above each says so. They pin the dialect guard and the word check.