refactor(store): use Record as Store generic

[timdeschryver]

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• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
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PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Closes #

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

This change should help for cases as #2780 (comment).
This change doesn't fix the cases where createFeatureSelector is used with 2 generics.
To resolve those cases, we could assert the generic T as any, or remove the <State, FeatureState> overload from createFeatureSelector in the next version.

export const selectBooksState = createFeatureSelector<State, BooksState>(
  booksFeatureKey
);

[ngrxbot]

Preview docs changes for 0092dd1 at https://previews.ngrx.io/pr3158-0092dd10/