Draft: Add manual reload to direnv layouts

Version Control Information

Source branch: feature/envrc-manual-layouts
Target branch: devel

Commits:

* direnv: add manual reload for nix layout

* direnv poetry: watch hash file

* direnv: use layout_dir

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## Description

_Feel free to add further information about your MR in this section_

Closes:  #

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## [Merge Prerequisites](https://gitlab.com/yaook/meta/-/wikis/Review-Guide)

* [ ] MR title (and description) are descriptive
* [ ] Code is readable and syntactically correct
* [ ] Code is understandable
* [ ] Documentation has been updated, if necessary
* [ ] [Commit messages look good](https://chris.beams.io/posts/git-commit/)
* [ ] [Release note](https://yaook.gitlab.io/k8s/devel/developer/guide/coding-guide.html#creation-of-release-notes) file in RST format added in latest commit

**As a developer**: please do not tick these boxes yourself. As a reviewer: please get yourself a ~hot~ cold beverage.