bug/medcat: CU-869bbj5u4 Fix core dependencies

[mart-r]

Currently, can't even import the base medcat package from a raw install due to it importing medcat.utils.check_for_updates which in turn uses packaging which isn't listed as a dep, let alone a core one.

Going further than that, there's a few other deps that are missing:

• medcat.utils.downloads_scripts needs requests
• medcat.utils.legacy.convert_meta_cat needs to explicitly specify it needs MetaCAT
• medcat.utils.legacy.convert_rel_cat needs to explicitly specify it needs RelCAT
• medcat.utils.regression.checking and medcat.utils.regression.regression_checker need pyyaml

So this PR does the following:

• Adds explicit checks for installed optional dependencies to medcat.utils.legacy.convert_meta_cat and medcat.utils.legacy.convert_rel_cat
• Add missing core dependencies
  • packaging
  • pyyaml
  • requets
• Adds a script that checks each import and categorises it
  • Importable in default / no-extras install
  • Explicitly raise the medcat.utils.MissingDependenciesError upon import
  • Failed to import due to some other error (if any exist, exits with non-zero exit status)
• Adds a workflow job that runs the check from above
  • Expects a zero exit status
  • Still provides the output

[tomolopolis]

Task linked: CU-869bbj5u4 Fix issues with base dependencies

To resolve this issue, add a permissions: block specifying the minimum required permissions to either the root of the workflow file or to each job. Since neither job requires write access to the repository or other privileged resources, a root-level block with contents: read is sufficient. This will apply contents: read to all jobs unless overridden. The change should be placed immediately after the name: and before the on: block (commonly, after line 1).