Convert limayaml functions to use pointer

[afbjorklund]

Add a simple unit test for some coverage

[afbjorklund]

Interesting failure, on Windows:

    validate_test.go:25: assertion failed: error is not nil: field `mounts[1].location` must be an absolute path, got "/tmp/lima"

Apparently using the "wrong" path.

i.e. it probably needs some TMPDIR

https://pkg.go.dev/os#TempDir

On Unix systems, it returns $TMPDIR if non-empty, else /tmp. On Windows, it uses GetTempPath, returning the first > non-empty value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory. On Plan 9, it returns /tmp.

[AkihiroSuda]

Could you explain the purpose of this?