Switch runtime from Alpine to Chimera

[Drsheppard01]

It is yet one experimental feature request

Why: Because mallocng from musl is underperfoming (see tests)
Chimera uses mimalloc instead standard allocator

Benefits: potentially faster AppImages
Risks: Chimera is still alpha, and repo is poor

It still requires a lot of performance testing

[TheAssassin]

The influence of the runtime code itself is rather small overall, most of it comes from libfuse. I'd rather avoid using unstable distros and binaries, though.

[probonopd]

@VHSgunzo says here:

I also tested AppImage type2-runtime (which is also now compiled on musl) and it too has a lower read speed than the squashfuse+glibc.

We should do some actual measurements before we jump to conclusions.

[probonopd]

Citing from over there:

the difference in my test was ~15%
squashfuse+glibc vs type2-runtime

Thanks for the test @VHSgunzo.