[EPIC] Fix how we handle updates to components

[petefoth]

Problem

The old model of an automatic updater:

• detected an updated component.;
• Downloaded the update;
• Committed it directly to the master branch ;
• Updated the .version_code of the component.

This is no longer appropriate because some components

• are too big to be stored in git, even using git-lfs (see microG Services v0.3.10 is over 100 MB and it will be rejected by GitHub #53 )
• need additional changes - e.g. to permissions files - in order to work (see New versions of microG components have 'broken' the build #36 )

Some issues have already been raised, and fixes implemented to deal with some of these issue,

• Change updater action to not commit direct to master branch #48 was raised, and (partially fixed) to stop updates being committed to master until they had been checked / tested
• Get microg GmsCore & FakeStore direct from GitHub not from this repo #65 introduced the vendorsetup.sh script, which, for the microG components, pulls the version of the component specified in .version_code directly from the component's github releases page, at build time.

Solution requirements

For all of the components included in this project:

1. the need for an update is detected automatically;
2. the new component can be tested before the repository code is changed to use the updated component;
3. the number of times a component is downloaded is minimised: github imposes bandwidth limits on projects it hosts (including the projects / components we use), and our use of those components should minimise how much of that bandwith we use.

Solution implementation

1. A 'Check for Updates` action checks whether new versions are available. If they are, for each compnent with an update, it creates an issue with the title 'Update to version '.
2. A project maintainer will 'fix' the issue, by trying the new component: if the new component is OK, the maintainer will commit a change to the .version_code file for the component, causing the vendorsetup.sh script to download the updated component at build time.
3. The issue will be closed, once a monthly build run is completed that includes the updated components.

[petefoth]

Thee is some good code that we can use in this PR

• this commit and this commit can be used to change vendorsetup.sh to pull F-Droid files as well as microG files

[petefoth]

Made this an EPIC as it has sub-issues. It can / will be closed when all sub-issues are resolved and closed