action: Initial package implementation and new RPC support

[austinvalle]

Related Issue

N/A

Description

This PR implements a skeleton of the new provider server RPCs defined in hashicorp/terraform-plugin-go#534 .

All the implementation currently does is map enough information needed for unlinked resources (to be implemented in a future PR). We also ignore deferred action/client capabilities for now, since the interfaces they will eventually be used with don't exist yet.

This PR also implements some plumbing necessary to retrieve/store schemas and actions on the framework provider server itself, which will be fully fleshed out and tested once a future PR hooks up GetProviderSchema and GetMetadata.

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Using the TODO:Actions tag to keep up with future unit testing and decisions to be made.

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

No

[bbasata]