Implement interfaces and framework for multi tenancy

[codeforall]

The PR aims towards building support for multi tenancy and contains multiple commits for the following.

• Establishing a Framework for Master Key.
• New Shared Cache Management Framework.
• Adding catalog table for managing key providers.
• Revamping the Keyring API Interface and Integrating Master Key.

Individual commit messages contain a more detailed description of changes.

[dAdAbird]

Do we need this PR anymore (having https://github.com/Percona-Lab/pg_tde/pull/121)?

[codeforall]

There is a new PR for the same. Closing this draft