Static TLS Configuration Store Library Implementation

[rmehta19]

This PR is a static implementation of the TLS Configuration Store Library. No calls to S2A are made.

A note on tls_config_store_test.go

• The 'Equal' function cannot be used to validate the contents of rootCertPool because it is not yet part of a go release(https://cs.opensource.google/go/go/+/4aacb7ff0f103d95a724a91736823f44aa599634). A solution could be to temporarily copy the implementation of 'Equal' in the master branch of the golang. However the implementation accesses fields from the x509.CertPool struct, which are lowercase, hence private. Therefore, in our package we cannot implement Equal by defining an alias of CertPool, because CertPool fields are private.

[matthewstevenson88]

Thanks for the PR Riya! It's looking great! Left a handful of mostly-minor comments. Should be good to go after that.

[rmehta19]

Thanks for the PR Riya! It's looking great! Left a handful of mostly-minor comments. Should be good to go after that.

Thanks for the review Matt!

[tavishvaidya]

Did a first pass, will do another one after all changes are in, thanks!

[rmehta19]

Did a first pass, will do another one after all changes are in, thanks!
Thanks Tavish!

[rmehta19]

Thanks for the comments! addressed them all in the latest push to this branch, let me know what you think!

[matthewstevenson88]

LGTM with a few minor nits.

Thanks for the PR Riya!