configitems: get default values from the central registry when available We do not have any registered config yet, but we are now ready to use them. For now we ignore this feature for config access with "alternates". On the long run, we expect alternates to be handled as "aliases" by the config item themself.

configitems: introduce a central registry for config option We now have the appropriate infrastructure to register config items. Usage will added in the next changeset.

configitems: add a basic class to hold config item information The goal of this class is allow explicit declaration for the available config option. This class will hold the data for one specific config item. To keep it simple we start centralizing the handling of the default config value. In the future we can expect more data to be carried on this class. For example: - documentation, - status (experimental, advanced, normal, deprecated), - aliases, - expected type, - etc...

run-tests: fix -i when "#testcases" is used in .t test The "#testcases" feature introduced by 7340465bd788 has issues with "-i" because "-i" uses "test.name.endswith('.t')" to test if a test is .t or not. test.name could now be something like "test-foo.t (caseA)" so the above endswith test is no longer valid. This patch changes the test to use "self.path" which won't have the issue.