chore: Uses pip-tools and dependabot to manage dependencies and versions

[saltiyazan]

Description

• Removes renovate and replaces it with dependabot to automate dependency version updates
• Replaces requirements.txt files with requirements.in, requirements.txt is generated using pip-tools"
• Bumps lxd version as 5.17/stable does not exist anymore

Files were generated using the following commands:

• pip-compile requirements.in
• pip-compile test-requirements.in -c requirements.txt

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have bumped the version of the library

[ghislainbourgeois]

I think we should use 5.0/stable here, as it is the LTS release. 5.19 support will be dropped when 5.22 is released.

[saltiyazan]

Default version used in setup-lxd is 5.0/stable. removed the channel parameter.