feat: convert entity and router selectors interfaces to types

[markostanimirovic]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

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

What is the current behavior?

Interfaces EntitySelectors and RouterStateSelectors are not compatible with Record<string, Selector> which is expected as createSelector.extraSelectors result. For example, we cannot add entity selectors to a specific feature in the following way:

export const productsFeature = createFeature({
  name: 'products',
  reducer: createReducer(initialState),
  extraSelectors: ({ selectProductsState }) =>
    adapter.getSelectors(selectProductsState) // compilation error
  ),
});

Workaround:

  extraSelectors: ({ selectProductsState }) => ({
    ...adapter.getSelectors(selectProductsState),
  }),

What is the new behavior?

Types EntitySelectors and RouterStateSelectors are compatible with Record<string, Selector> and there is no compilation error in the example above.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

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[timdeschryver]

Thanks for the added tests!