[Stacks Actions] Update protobuf protocols to add Action Invocation support

[mutahhir]

RFC: https://hermes.hashicorp.services/document/1qNke5ZCTNMQIw-rPietiHbHlV0zJELDtDftTeN2RjVc?draft=true
Jira: https://hashicorp.atlassian.net/browse/TF-33014

Includes Stacks protobuf changes that allow Action invocations (lifecycle triggered only) to be sent to the TFC Agent. This is just the protocol changes, and does not add the code that uses the updated protocol.

This PR is part of multiple (in order):

Terraform

• This PR
• Plan Action Invocations
• Deferred Action Invocations
• Apply Action Invocations
• TBD: Apply Deferred Action Invocations

TFC Agent

• Plan Action Invocations Support
• Apply Action Invocations Support

Atlas

• Plan Action Invocations Support
• Link missing for Apply Atlas

Target Release

1.15.x

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

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.