HHH-20128: Spanner PG: Configure Locking Strategy, CTE, Temporary Tables

[sakthivelmanii]

[Please describe here what your change is about]

1. Configure Locking Support for Spanner
2. Configure minimum PG version
3. Fixes CTE related issues
4. Configure strategy for mutations

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license
and can be relicensed under the terms of the LGPL v2.1 license in the future at the maintainers' discretion.
For more information on licensing, please check here.

---

---

Please make sure that the following tasks are completed:
Tasks specific to HHH-20128 (Sub-task):

• Add test OR check there is no need for a test
• Update documentation as relevant: javadoc for changed API, documentation/src/main/asciidoc/userguide for all features, documentation/src/main/asciidoc/introduction for main features, links from existing documentation
• Add entries as relevant to migration-guide.adoc (breaking changes) and whats-new.adoc (new features/improvements)

https://hibernate.atlassian.net/browse/HHH-20128

[sakthivelmanii]

@beikov can you please check and merge this?