fix(gateway-api): retry CRD discovery on transient errors

fix(gateway-api): retry CRD discovery on transient errors

Add retry with exponential backoff for Gateway API CRD discovery to handle
transient API server errors during operator startup. This prevents permanent
failure of Gateway API TLS termination when API server is temporarily
unreachable.

Changes:
- Extract preconditions into private hive component (cell.ProvidePrivate)
- Add isTransientError() to distinguish retryable vs permanent errors
- Configure backoff with 200ms-5s range and 30s context timeout
- Report health status during retry attempts
- Ensure consistent behavior between initGatewayAPIController and
  registerSecretSync by sharing preconditions

Fixes: #43130
Co-authored-by: Claude <noreply@anthropic.com>
Signed-off-by: Aleksei Sviridkin <f@lex.la>