Use new string APIs and add memory safety for PyWinObject_AsPARAM

[mhammond]

This shamelessly steals the PARAM handling from @kxrob's #1860 - renamed and reformatted etc, but I Think this looks good.

[kxrob]

I cherry-picked my corresponding previous draft patch (and an old pending fixup) on the parent of this PR to see the effective diff:
The new extra PyWinObject_AsSimplePARAM in those ~5 locations are more clear, faster. (The old specific error messages are not necessary.)
The PyWin_PARAMHolder now also can hold a PyWinBufferView from AsPARAM(). See extra review comment regarding potential speed issue.
Otherwise it seems mostly alike and looks good to me.

The first Py3.12 alpha should appear in October on github for testing the #1860 deprecation replacements fully - the PR coverage should be mostly complete.

[mhammond]

Thanks for the review!