[ENH,DEP] Update .ts writer and deprecate old writers

[MatthewMiddlehurst]

Updates and renames .ts file writer. I have been using this function recently and it is pretty inconvenient when writing different train and test files for the same problem or folds. It is also missing some of the metadata options.

Uses all the new(?) validation and conversion functions rather than doing it itself, so now it accepts all the different collections. It all just gets converted to np-list anyway.

Deprecates the old version and arff writer. The arff writer only works for univariate equal length classification and I dont really know if anyone uses the format for time series anymore. There are much better ways for that now and .ts has much more functionality..

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I have added the following labels to this PR based on the title: [ deprecation, enhancement ].
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