psalm-types for complex service/extension/factory type hints.

[Chrico]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [x] Tests for the changes have been added (for bug fixes/features)
• [x] Docs have been added/updated (for bug fixes/features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This PR does introduce 2 new psalm-types for:

• Service --> callable(ContainerInterface $container):mixed
• ExtendingService -> callable(mixed $service, ContainerInterface $container):mixed

and centrailizes the definition to reuse it in ReadOnlyContainer and ContainerConfigurator

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.97%. Comparing base (feaa4d0) to head (2c50cb6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #46 +/- ## ========================================= Coverage 98.97% 98.97% Complexity 217 217 ========================================= Files 10 10 Lines 588 588 ========================================= Hits 582 582 Misses 6 6 ``` | [Flag](https://app.codecov.io/gh/inpsyde/modularity/pull/46/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=inpsyde) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/inpsyde/modularity/pull/46/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=inpsyde) | `98.97% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=inpsyde#carryforward-flags-in-the-pull-request-comment) to find out more.

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