Edits and improvements to the reusable build workflow

[filterpaper]

• Add artifact_name as a workflow dispatch option. Users can specify a different output artifact name alongside custom build and config path.
• Use set -x for verbose output of shell commands. This will display content of all environment variables and aid troubleshooting.
• Simplify grep one-liner command for displaying Kconfig file.
• Steps naming consistency.
• Shell if then statement consistency.

[joelspadin]

Seems reasonable to me.

[petejohanson]

Thanks!