Modify distribution results page to show isolated workflows

[jdolitsky]

New changes have landed in the conformance tests allowing for executing just a single workflow. In order to provide better insight in the green/red status of a given registry for each of these workflows, the GitHub actions definitions have been split into 4 parts to test each workflow individually.

Due to the growing size of the markdown table, made significant improvements to the results page README and now display one table per registry.

Lastly, in order to not overload GitHub actions with multiple runs at 6AM UTC, the cron schedule for each registry has been made unique (each 5 minutes apart, alphabetically).

[jdolitsky]

Here is an example of what this will look like: https://bloodorangeio.github.io/oci-conformance/distribution-spec/

[jdolitsky]

Added some language at the top of the results page to share that the automated workflows are not "official" results:

Should be good to merge. Once this is in we just need to plug in necessary credentials for each registry.

cc @caniszczyk