CBP-18302: allow absolute URL in repository input

[mgoltzsche]

...instead of supporting only the short form syntax ({owner}/{repo})

Additional changes:

• Allow cloning from arbitrary SSH URL instead of conditionally letting the action generate the SSH URL from the given short form URL internally.
• Fix a bug where an invalid commit-url output value was generated when cloning a repository from Bitbucket Datacenter (the workflow originating SCM provider URL was always used as base URL instead of using the bitbucket-server-url value and there was a missing slash).

[mgoltzsche]

I rebased the PR now to include #41.

[mgoltzsche]

While e2e testing the action I realized that the logic that uses the commit SHA the workflow originates from as commit SHA of the repo to checkout by default when the checkout action's repository value is equal to the one within the SCM event (the one the workflow originates from) broke since the event may contain the repository URL in a different format. Thus, the repository URL from the SCM event also needs to be normalized before comparing it to the one within the repository action input...

I'll also add corresponding e2e tests to the workflow within this repository...

[mgoltzsche]

Instead of normalizing the repo URL from the SCM event before comparing it with the repository input, I made the code not modify the repository input in the first place since the default will always equals the value from the SCM event. To have the initial validation and input normalization logic testable using the new set of tests, I added an internal repositoryCloneURL field which holds the normalized version of the repository input from where the code obtains it subsequently where appropriate.