[perf] migrate slow operations to non-blocking calls

We're doing a lot of long-running processing on the UI thread which is

1. hurting performance, and
2. spamming the logs (distracting users as in https://github.com/flutter/flutter-intellij/issues/7151, https://github.com/flutter/flutter-intellij/issues/7641 and https://github.com/flutter/flutter-intellij/issues/8083)

We've had issues safely making the change to use the prescribed `ReadAction.nonBlocking` APIs (see for example: https://github.com/flutter/flutter-intellij/issues/7792) so we'll want to proceed thoughtfully.

This issue will stand as a tracker for migrations.

Some resources:

* 📖 [plugin docs](https://plugins.jetbrains.com/docs/intellij/threading-model.html#avoiding-ui-freezes)
* 📖 [ReadAction.java](https://github.com/JetBrains/intellij-community/blob/idea/251.23774.435/platform/core-api/src/com/intellij/openapi/application/ReadAction.java)

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Blocking calls to migrate:

- [x] #8093
- [x] https://github.com/flutter/flutter-intellij/pull/8094
- [x] https://github.com/flutter/flutter-intellij/pull/8095
- [x] `io.flutter.bazel.WorkspaceCache#refresh`
- [x] https://github.com/flutter/flutter-intellij/issues/8083
- [ ] `io.flutter.run.SdkRunConfig#getState`