🧪 improve some tests

[chrisjsewell]

• condense broken doc tests into single module
• condense api tests into single module
• remove unnecessary test projects when doc_basic can be used
• add testing of signature capture to add_sections_sigs test project

[codecov[bot]]

Codecov Report

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

Project coverage is 86.94%. Comparing base (4e10030) to head (d769707). Report is 49 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1301 +/- ## ========================================== + Coverage 86.87% 86.94% +0.06% ========================================== Files 56 60 +4 Lines 6532 6915 +383 ========================================== + Hits 5675 6012 +337 - Misses 857 903 +46 ``` | [Flag](https://app.codecov.io/gh/useblocks/sphinx-needs/pull/1301/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=useblocks) | Coverage Δ | | |---|---|---| | [pytests](https://app.codecov.io/gh/useblocks/sphinx-needs/pull/1301/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=useblocks) | `86.94% <100.00%> (+0.06%)` | :arrow_up: | 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=useblocks#carryforward-flags-in-the-pull-request-comment) to find out more.

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