add MU plugin that disables two site health status tests 'conflicting' with bedrock

[Levdbas]

The PR removes the two Site Health Status notifications highlighted in red in the screenshot.

• Auto updates test, mentioned by @retlehs in WordPress Site Health reports 'Should be improved' on default Bedrock install #522 since Bedrock discourages auto-update by design, we disable the background_updates check.
• Theme update check , mentioned by @yangm97 in WordPress Site Health reports 'Should be improved' on default Bedrock install #522 By disabling theme_version we disable the test that checks if there is a default theme available, the default 'default theme' is twentytwenty. Since most bedrock installs will probably come without this default theme, this triggers the advice.
  As a side effect the actual theme update checks aren't done as well. So I am not sure if disabling this test is the way to go.

The code run by the theme_version check can be found here

This is my first PR attempt for a Roots project. So let me know if I missed something or something can be improved.

[swalkinshaw]

As another option, could we instead change the label and categorization of them? This is still probably a good solution, just wondering if it's better to leave them (so people know about their existence) but call out why they are "disabled".

[Levdbas]

I think this would've been nice, but unfortunately the site_status_tests hook only lets you add test or remove existing tests, see https://developer.wordpress.org/reference/hooks/site_status_tests/ for the documentation and some examples for this hook.

The only 'workaround' would be to remove these mentioned tests and add new ones specific for a Bedrock installation. Now that I am brainstorming about this idea: For example a test that checks the WP_ENV constant and warns if the site is not on a subdomain and still has the WP_ENV on staging.

There are possibilities but out of the scope of this PR. But might be a nice thing to consider for increasing the UX/DX.

[retlehs]

If you want to make a Composer package out of this I'd be happy to add it to our docs, but this isn't something we will be adding in Bedrock at this time