Support MATLAB Table and Timetable saved with MATLAB >2025a

[foreverallama]

Since 2025a, MATLAB increased the variable name character limit for their tables to 2048 characters. This is accompanied by new properties useVariableNames2048, with the legacy field carrying a truncated name.

This PR bumps the load version for MATLAB tables to v5 by supporting these new fields with long variable names and dimension names. The save version remains v4.

As a side note, this probably means that v4 does not support long variable names. I am yet to test this out by saving from Python with Table v4 and loading back in MATLAB.

[foreverallama]

MATLAB release notes states the following:

In tables and timetables, the maximum allowed length of dimension and variable names has increased
to 2048 characters. This length matches the updated maximum identifier length, which you can query
by using the namelengthmax function.
If you save a table or timetable with long dimension or variable names to a MAT file, then you can
load it into a MATLAB release before R2025a. However, the earlier MATLAB release truncates the
long dimension and variable names in the table or timetable to 63 characters.

I'll be checking with timetable as well before proceeding further with this PR. Regarding the compatibility, I tried out the following:

long_name_1 = "X" * 100
long_name_2 = "Y" * 100

df = pd.DataFrame({
    long_name_1: [10.0, 20.0, 30.0],
    long_name_2: [100.0, 200.0, 300.0],
})

mdict = {"table_var_names": df}
save_to_mat("test.mat", mdict, version="v7")

I was surprisingly able to load this with the full variable name with MATLAB 2025b. Not sure how the behaviour would change with earlier releases (<2025a) though. Hopefully it doesn't error out and just truncates the length.

[foreverallama]

Timetable has also bumped to version 7, with the same changes as Table. This PR now supports loading both Tables and Timetables saved with MATLAB >2025a.

The tests should fail because of NumPy 2.5, so I'll keep this open till that is fixed.