Add actions to the apply graph

[DanielMSchmidt]

This PR adds actions to the apply graph. There are a bunch of features within actions missing (conditions / provider attribute) and a lot of tests missing, but this should build a good basis to expand from.

Fixes TF-25937

Target Release

1.14.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.

[mildwonkey]

I'm curious about this - Triggers and Events are configuration constructs that don't apply to CLI triggered actions, so I wouldn't expect them to be included at all with a CLI triggered action. How is this info getting used? (I'm worried it'll be confusing if we present info about events and triggers for a CLI-invoked action which has neither of these)

[DanielMSchmidt]

This info is being used a) for constructing the apply graph and b) to display when we render the plan.
I'm also not 100% happy with the structure here. When building the prototype I experimented with a oneof solution differentiating between CLI and lifecycle triggered actions but that was creating a lot of boilerplate so I went with a flat structure here. I think in the renderer and apply graph we can check if the trigger event is CLI and if that's the case we don't read the other fields.

We can change the approach though at any time, so if we find this to be really annoying when building the terraform invoke command we can still adjust :)

[mildwonkey]

I left a couple of tiny comments but things look solid to me - I don't feel confident approving this, but that's not because I have major concerns.