The previous commit for MDEV-32884 fixed the s3_protocol_version option,
which was previous only using "Auto", no matter what it was set to. This
patch does several things to keep the old behaviour whilst correcting
for new behaviour and laying the groundwork for the future. This
includes:

* `Original` now means v2 protocol, which it would have been due to the
  option not working, so upgrades will stil work.
* A new `Legacy` option has been added to mean v1 protocol.
* Options `Path` and `Domain` have been added, these will be the only
  two options apart from `Auto` in a future release, and are more
  aligned with what this variable means.
* Fixed the s3.debug test so that it works with v2 protocol.
* Fixed the s3.amazon test so that it works with region subdomains.
* Added additional modes to the s3.amazon test.
* Added s3.not_amazon test for the remaining modes.

This replaces PR #2902.