bug(connections): URL parser does not set useSSL for sslmode=verify-ca and verify-full

[ZhuchkaTriplesix]

connection_url_parser.dart only sets useSSL = true for sslmode values true, require, and prefer. The valid driver values verify-ca and verify-full are ignored.

Impact: Persisted use_ssl flag is misleadingly false even when the URI explicitly requests verified TLS. UI, future diagnostics, and any code that trusts the flag may make wrong assumptions.

Expected: verify-ca and verify-full must set useSSL = true.

Acceptance criteria:

• Parser maps verify-ca, verify-full, require, and true to useSSL = true.
• disable sets useSSL = false.
• Add unit tests for each mode.