Test: make store/state machine tests rt-agnostic

[SteveLauC]

What does this PR do

Based on the discussion in this thread, turning test_all() and test_store() asynchronous to make the log tests runtime-agnostic.

Checklist

• Updated guide with pertinent info (may not always apply).
• Squash down commits to one or two logical commits which clearly describe the work you've done.
• Unittest is a friend:)

---

This change is 

[SteveLauC]

openraft/src/docs/getting_started/getting-started.md line 183 at r1 (raw file):

To test your implementation, you have two options:

1. Run `Suite::test_all()` with an `async fn()` that creates a new pair of [`RaftLogStorage`] and [`RaftStateMachine`],

impl StoreBuilder for Fn has been removed in this commit, so this approach no longer works.

[drmingdrmer]

Reviewed 10 of 10 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion

[drmingdrmer]

Reviewable status: all files reviewed, 1 unresolved discussion