Remove UxDataArray.data_location

[rajeeja]

Closes #1748. data_mapping already returns the same information and is what plot.points() uses, so this drops data_location, moves its docstring onto data_mapping, and updates the two error messages that referenced it. Note data_location shipped in v2026.07.0 through v2026.09.0.

[Sevans711]

Looks like a clean fix to me! Removes all instances of data_location and sets a reasonable precedent for how to rephrase error messages that previously contained data_location.

Slightly more context: after some internal discussions regarding the PR and comment linked above, it was decided that data_location should be removed because it was fully redundant with data_mapping and was introduced much more recently (only a few months instead of almost 2 years). It should be okay to proceed without a deprecation cycle because it was introduced so recently, and we don't think that any users will have started using it yet (any users who needed this functionality would most likely have been using data_mapping already).

Sidenote: #1678 will require some substantive updates after this merges, because it added lots of new error message text containing data_location, but it can just follow the pattern introduced here using data_mapping instead.