* Sema: implement linksection on functions
* Implement function linksection in Sema.
* Don't clobber function linksection/align/addrspace in Sema.
* Fix copy-paste typo in tests.
* Add a bunch of missing test_step.dependOn.
* Fix checkInSymtab match.
Closes#12546
Move common tests by target file format (Wasm, MachO) into helper
functions in `link.zig`, and sort alphabetically within for easier
tracking versus file organization on disk.