ci: run compio-buf and compio-io tests under miri

[FalkWoldmann]

This is similar to the other miri action pipeline. I ignored the tests with the known soundness issues

[FalkWoldmann]

Differences to the executor miri job:

• Runs on one ubuntu runner and lets miri interpret the other targets, which also covers 32-bit and big-endian
• Uses cargo miri nextest run for parallel tests
• Sets -Zmiri-strict-provenance and runs cargo miri setup separately, as the miri README suggests.
• cargo update -p rustix --precise 1.1.4 is temporary: rustix 1.1.5 doesn't build with only net (net feature alone fails to compile in 1.1.5: sockopt uses crate::timespec, which net does not gate in bytecodealliance/rustix#1689). Can go once Compile timespec for net feature bytecodealliance/rustix#1681 is released.

If u prefer a more homogeneous setup wrt. to the other miri pipeline, I can streamline either one :)