Improvements to the build system

[dime10]

After #1588 and #1589, there are a few issues still present in the build systems. This issue lists them here to not forget:

• [mlir] test ASAN config on different systems
• [mlir] fix existing ASAN issues
• [mlir] clean up build output of non-core build targets (llmv, mlir-hlo, enzyme, plugin)
• [mlir] do not build and link plugin targets every time, which currently adds significant overhead to the make catalyst command
• [frontend] resolve any warnings in the Python test suite (fix or silence)
• [frontend] resolve any XPass tests
• [frontend] ensure C++ builds from the frontend use the correct compiler setup
  • For instance, the lapack kernel builds triggered from setup.py will pick an arbitrary compiler. On the AWS machine with gcc-9 available (on top of other compilers), it will pick that one. This leads to a failure to build the python package due to the "-std=c++20" flags which aren't supported by the picked compiler.
• [frontend] do not use python3.10 by default in the frontend lit config
• enable ASAN CI builds on PRs
• enable both Clang and GCC CI builds on PRs
• remove OpenMP dependency (I think it might unused now)

Lower down the priority list:

• speed up handful of unusually slow pytests (likely the mcm one-shot tests)?
• unify C++ code coverage tools (gcov on linux vs llvm-cov on mac)
• unify sourcing of gtest (both llvm-style unit tests and stim depend on it, the latter currently raises a warning about missing gtest)