xenomai: Add distro and recipe for Xenomai 4 on x86

[leograba]

Add a distro named "torizon-xenomai" that select the Xenomai kernel and set the corresponding kernel command-line args.

Add a recipe that build the "linux-evl" Xenomai 4 kernel fork, which include the EVL co-processor implementation.

Use the active SLTS kernel 5.10.y branch from Xenomai, because it's the same version as "linux-intel-lts" for kirkstone in meta-common-torizon.

Set minimal kernel config for Xenomai to work. Further optimization may be possible, but is not covered.

[microhobby]

LGTM! Xenomorph cherry picked! Thanks @leograba

I had to cherry-pick because the repo needed a sync with upstream, and this mess up with the hashes. But you commit is here: 206f06b40510f7993dc9fc7156248dfb1f9ab5aa

[leograba]

lol thanks man!