Override $identitySelect for CockroachDB adapter

[bpamiri]

Summary

• CockroachDB inherits PostgreSQL's $identitySelect() which uses pg_get_serial_sequence() and currval() — neither of which CockroachDB supports
• Overrides the method in CockroachDBModel.cfc with a MAX-based query, since CockroachDB's unique_rowid() generates monotonically increasing values
• Follows the same pattern used by the Oracle adapter, with BoxLang compatibility from the PostgreSQL adapter

Closes #1971

Test plan

• Verify model("Foo").create(...) returns the correct primary key on CockroachDB
• Verify explicit PK inserts still work (no identity select triggered)
• Confirm no regression on PostgreSQL (parent adapter unchanged)

🤖 Generated with Claude Code

[github-actions]

Wheels Test Matrix

Engine	MySQL	PostgreSQL	SQL Server	H2	Oracle	SQLite
lucee5	✅	✅	✅	✅	✅	✅
lucee6	✅	✅	✅	✅	✅	✅
lucee7	✅	✅	✅	✅	✅	✅
adobe2018	✅	✅	✅	--	✅	--
adobe2021	✅	✅	✅	--	✅	✅
adobe2023	✅	✅	✅	--	✅	✅
adobe2025	✅	✅	✅	--	✅	✅
boxlang	✅	✅	✅	--	✅	✅

Results for commit 2828efa.

[github-actions]

Wheels Test Results

    42 files  ±0   3 906 suites  ±0   25m 11s ⏱️ -25s
79 512 tests ±0  79 124 ✅ ±0  388 💤 ±0  0 ❌ ±0 
82 158 runs  ±0  81 770 ✅ ±0  388 💤 ±0  0 ❌ ±0 

Results for commit 066a10f. ± Comparison against base commit e57ecf8.

♻️ This comment has been updated with latest results.

[bpamiri]

Closing in favor of #1896's RETURNING-based approach, which avoids the race condition inherent in SELECT MAX(pk).