qemu, runInLinuxVM: change default cpu to qemu64
qemu, runInLinuxVM: change default cpu to qemu64

The flag -cpu max leaves QEMU 6.1.0 stuck on some systems,
for example when /dev/kvm is not read-writable.
This does not happen with -cpu qemu64.

Getting stuck like that is a regression in 6.1.0 not yet present in 6.0.0
and should be fixed with 6.2.0 according to early testing with rc1.

We should consider reverting this change when we merge QEMU 6.2.0.
See #146526.

fixes #141596

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