Fixes #24789: Archive API for import/export doesn't know about technique

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https://issues.rudder.io/issues/24789

This PR introduces import and export of categories for technique.
It add a new file descriptors for them, category.json which mimics category.xml but in JSON for consistency with other file format in archive.
Since category information where not updatable by API (internal or rest) up until now, I needed to also add the relevant logic to actually save changes in `/var/rudder/configuration-repository

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PR updated with a new commit

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PR updated with a new commit

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There's a test in error on CI that I don't seem to have locally, it needs a new pass of work:

[2024-06-26T12:22:30.325Z] Tests in error: 

[2024-06-26T12:22:30.325Z]   The test lib should::save a category should::create a new file and commit if the category
does not exist(com.normation.cfclerk.services.JGitRepositoryTest): Chained(error when committing technique 
category 'techniques/systemSettings/myNewCategory/category.xml',SystemError(An error 
occurred,java.nio.file.FileSystemException: /tmp/test-jgit-2024-06-26T14:22:13.809+02:00/techniques/systemSettings/
myNewCategory: Operation not permitted))

[2024-06-26T12:22:30.326Z]   The test lib should::save a category should::does nothing when the category already 
exsits(com.normation.cfclerk.services.JGitRepositoryTest): Chained(error when committing technique category 
'techniques/systemSettings/myNewCategory/category.xml',SystemError(An error 
occurred,java.nio.file.FileSystemException: /tmp/test-jgit-2024-06-26T14:22:13.809+02:00/techniques/systemSettings/
myNewCategory: Operation not permitted))

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PR updated with a new commit