[QA] get rid of `$SPACE_ID_FROM_OCIS` and use space name to determine the working space

[saw-jan]

Variable $SPACE_ID_FROM_OCIS was introduced while we were running API tests from the core repo. Using global var to determine in which space we are working on during the test will be problematic and might bring indeterministic behavior in the scenario. https://github.com/owncloud/ocis/blob/ff0ac7e06999196f6668778d40db3826d38bbf0e/tests/TestHelpers/WebDavHelper.php#L43

So to prevent this, let's use the space name to determine the working space and get rid of global var. NOTE: default to space Personal (helpful for coreAPI test suites) if space name is not provided or used.

These methods could be useful:

• rememberTheAvailableSpaces()
• setAvailableSpaces()
• getAvailableSpaces()
• getCreatedSpace()
• addCreatedSpace()