Add branch field to module entries in modules.json to record what branch a module comes from

[ErikDanielsson]

As I reported in #1728, the commands that rely on version information in the modules.json fail if a module was installed from a branch other than the default branch. I've fixed this by adding branch information to the module entries in the modules.json. The updated modules.json looks something like this

{
    "name": "a/pipeline",
    "homePage": "https://a-pipeline.com",
    "repos": {
        "some/cool/repo": {
            "base_path": "modules",
            "git_url": "https://git-provider.com/some/cool/repo.git",
            "modules": {
                "first-modules": {
                    "git_sha": "<some sha>",
                    "branch": "main"
                },
                "second/module": {
                    "git_sha": "<another sha>",
                    "branch": "other-branch"
                }
            }
        }
    }
}

To add this feature I needed to refactor the check_up_to_date method in modules_json.py since it was to big and unruly to be modified directly.

The new feature is tested using a new branch-tester branch in the nf-core/modules-test repository on gitlab.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #1738 (7b72ecf) into dev (bc935ba) will increase coverage by 0.20%.
The diff coverage is 66.06%.

@@            Coverage Diff             @@
##              dev    #1738      +/-   ##
==========================================
+ Coverage   68.24%   68.44%   +0.20%     
==========================================
  Files          59       59              
  Lines        7075     7141      +66     
==========================================
+ Hits         4828     4888      +60     
- Misses       2247     2253       +6     

Impacted Files	Coverage Δ
nf_core/__main__.py	52.66% <0.00%> (ø)
nf_core/modules/list.py	71.23% <ø> (ø)
nf_core/utils.py	80.77% <50.00%> (-0.32%)	⬇️
nf_core/lint/modules_json.py	76.66% <60.00%> (-4.11%)	⬇️
nf_core/modules/modules_json.py	72.05% <64.05%> (+6.22%)	⬆️
nf_core/modules/patch.py	80.70% <66.66%> (-0.78%)	⬇️
nf_core/modules/update.py	76.08% <69.04%> (-2.29%)	⬇️
nf_core/modules/modules_repo.py	82.38% <86.66%> (+0.39%)	⬆️
nf_core/modules/lint/module_changes.py	50.00% <0.00%> (-2.39%)	⬇️
nf_core/modules/lint/module_patch.py	10.66% <0.00%> (-2.33%)	⬇️
... and 6 more

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[mirpedrol]

Looks good :)
Only a couple of minor comments.

[ErikDanielsson]

Thanks for the review @mirpedrol!