Many tests didn't change back from subdirectories at the end of the tests ...
and they don't have to. The missing 'cd ..' could always be added when another
test case is added to the test file.
This change do that tests (99.5%) consistently end up in $TESTDIR where they
started, thus making it simpler to extend them or move them around.
For filelogs, debugindex and debugdata can be called with the file name
directly instead of the path to the revlog. Since in the future filelogs
will no longer be valid revlogs, calling with a path to the revlog is
deprecated for debugdata. For debugindex it is expected to still work,
but I changed them as well for consistency.
