Fixes #113216.

#112011 apparently broke builtin_zstd=no, because I had used parts of the Zstandard API that are considered "advanced", which are liable to have their signature changed at some point in the future. This means you need to build Zstandard with ZSTD_STATIC_LINKING_ONLY, which the built-in one does, but which you obviously can't do with a system-provided libzstd.

This fixes that by replacing ZSTD_findDecompressedSize with ZSTD_getFrameContentSize, which should work just as well. It might perhaps cause issues if we ever switch to using streaming compression instead, but I believe ZSTD_CCtx_setPledgedSrcSize should mitigate that (which I threw in already for good measure).

I also had to replace ZSTD_getParams and ZSTD_CCtx_setParams with individually setting the parameters using ZSTD_CCtx_setParameter. When stepping through the compression in a debugger it seems Zstandard effectively ends up calling ZSTD_getParams under the hood anyway, using whatever overrides you've provided through ZSTD_CCtx_setParameter, so this made no functional difference at all.

I've confirmed that this builds with builtin_zstd=no on Fedora 42.