Some miscellaneous test suite cleanups (#25256)

* test: remove test-compare-output and test-asm-link tests

These were low value and unfocused tests. We already have coverage of the
important aspects of these tests elsewhere. Additionally, there was really no
need for these to have their own test harness.

* test: rename issue_8550 standalone test to compile_asm

* test: rename backend=stage2 to backend=selfhosted, and add backend=auto

backend=auto (now the default if backend is omitted) means to let the compiler
pick whatever backend it wants as the default. This is important for platforms
where we don't yet have a self-hosted backend, such as loongarch64.

Also purge a bunch of redundant target=native.

* test: delete old stage1 compile_errors tests

generic_function_returning_opaque_type.zig was salvaged as it's still worth
having.

* test: pull tests in test/cases/llvm/ up to test/cases/

There is nothing inherently LLVM-specific about any of these.

* test: remove @cImport usage in interdependent_static_c_libs

* test: move glibc_compat from link to standalone tests

This is not really testing the linker.

* build: -Dskip-translate-c now implies -Dskip-run-translated-c

* build: skip test-cimport when -Dskip-translate-c is given

0 files changed, 0 insertions, 0 deletions