cmd/egg: Fix run and test command to accept kernel as argument and qemu options from QEMU_OPTS env var

[icexin]

Thanks for @prologic 's contribution.

The following adjustments have been made on the basis of the original code:

• The binary files generated by egg test and egg run are placed in the temporary directory to keep the source code directory clean
• Modify the code of magefile.go to synchronize with the egg command