fix(store): `dispatch` return observable should be `<void>`

[arturovt]

This commit updates all dispatch signatures to return Observable<void>. Initially, the signature was intended to be void, but historically, it was returning Observable<any>, where any represents the state snapshot.

This is a breaking change. We've been delaying this fix for years, but now all the necessary changes should finally be made to allow us to progress with the NGXS code itself. It's especially important to clean up old planned todos as well.

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✅ Successfully ran 4 targets

- [`nx run-many --target=test --all --configuration=ci --maxWorkers=4`](https://cloud.nx.app/runs/Jv0SfxJfLX?utm_source=pull-request&utm_medium=comment) - [`nx run-many --target=lint --all`](https://cloud.nx.app/runs/XdHYP7lfTk?utm_source=pull-request&utm_medium=comment) - [`nx lint-types store`](https://cloud.nx.app/runs/GvzlTGDnnD?utm_source=pull-request&utm_medium=comment) - [`nx run-many --target=build --all`](https://cloud.nx.app/runs/aYbdMhUsqI?utm_source=pull-request&utm_medium=comment)

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[bundlemon[bot]]

BundleMon (Integration Projects)

Unchanged files (2)

Status | Path | Size | Limits :------------: | ------------ | :------------: | :------------: :white_check_mark: | Main bundles(Gzip)
_{hello-world-ng17/dist-integration/main.(hash)
.js}
| 68.38KB | +1% :white_check_mark: | Main bundles(Gzip)
_{hello-world-ng16/dist-integration/main.(hash)
.js}
| 66.87KB | +1%

No change in files bundle size

Final result: :white_check_mark:

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Current branch size history | Target branch size history

[codeclimate[bot]]

Code Climate has analyzed commit 5f4992ec and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 93.3% (50% is the threshold).

This pull request will bring the total coverage in the repository to 95.5% (0.0% change).

View more on Code Climate.