feat: add elastic pool reference support to MSSQLDatabase

Add elasticPoolIdRef/elasticPoolIdSelector fields to MSSQLDatabase,
allowing users to declaratively reference an MSSQLElasticPool resource
instead of hard-coding the Azure resource ID.

Changes:
- Add elastic_pool_id reference config for both cluster and namespaced
  providers pointing to azurerm_mssql_elasticpool
- Backport reference fields to v1beta1 storage version
- Regenerate CRDs, types, resolvers, and deepcopy methods
- Rewrite examples following the proven elastic pool pattern with
  unique resource names and labels to avoid E2E test conflicts
- Add MSSQLElasticPool to examples to test the new reference

Fixes #1197

Signed-off-by: Nicola <nicola.macoir@rightcrowd.com>

Author: nicolamacoir