portextract: add use_zstd option for .tar.zst distfiles

[herbygillot]

Adds native support for extracting zstandard-compressed distfiles via a new use_zstd option, following the same pattern as use_xz, use_lzip, etc. The zstd binary is located at runtime via PATH (same approach as lzip and 7za, since zstd is not a macOS system tool).

• portextract.tcl: add use_zstd to all_use_options; wire up get_extract_cmd (binaryInPath zstd), get_extract_suffix (.tar.zst), and add_extract_deps (bin:zstd:zstd)
• doc/portfile.7: document use_zstd between use_xz and use_7z
• tests/portextract.test: new test file covering get_extract_suffix and get_extract_pre_args for all use_* options, plus a mocked get_extract_cmd test for use_zstd

Closes: https://trac.macports.org/ticket/72713

[jmroot]

I think we were wanting to avoid adding any more use_* options, and instead move in the direction of figuring out the extract command automatically from extract.suffix. See discussion in #50969 and #64960.
@ryandesign @mojca @raimue

[herbygillot]

I think we were wanting to avoid adding any more use_* options, and instead move in the direction of figuring out the extract command automatically from extract.suffix. See discussion in #50969 and #64960. @ryandesign @mojca @raimue

OK, closing this in preference of file_extract - PR for that here: #402

[ryandesign]

I don't recall a discussion about not wanting to add new use_* options. A generic extract-any-file feature would be great and having it replace the use_* options is the ultimate goal but there were many design questions that I don't think were answered yet and in the interim I'm not opposed to the straightforward addition of a new use_zstd option.