fix: add resolve_quickemu() to quickget so it can locate quickemu

[flexiondotorg]

Description

quickget calls and references quickemu. The patch adds resolve_quickemu() to locate where quickemu is; either in the PATH will a fallback to the current working directory.

• Resolves bug: quickget does not find quickemu using which #1278

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• I have performed a self-review of my code
• I have tested my code in common scenarios and confirmed there are no regressions
• I have added comments to my code, particularly in hard-to-understand sections