Fix Oracle ALTER COLUMN syntax for Element identifiers

[jogibear9988]

Oracle interprets the valid column name Element as syntax in an unparenthesized ALTER TABLE ... MODIFY clause. KCC COMMON migration 196 fails with ORA-00903 while removing its default, then ORA-01735 when changing its type.

Use MODIFY (...) for both default removal and column changes. Existing identifier quoting remains in place. Two live Oracle regression cases verify direct default removal and removal through ChangeColumn, preserving existing values and checking that subsequent inserts receive NULL.

Validation:

• Both new cases failed against master before the fix and pass afterward against the configured Oracle instance.
• Local Unit and SQLite suites: 382 passed, zero failures or skips.
• Oracle CI passed. All other database matrix jobs passed except Sybase, where nine cases failed creating databases because MODEL was in use; the complete-coverage job was consequently skipped.
• KCC full Oracle migration chain (COMMON, VISU, MFCV2, WMS) plus two data-preservation regression cases: 3 passed. KCC also needs explicit Oracle index and LOB-conversion adaptations, kept in its separate repository.

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