feat: Add feature to enable dynamic instance types via workflow labels

[npalm]

Description

This PR adds an option to define the required instance type via the workflow labels. This could be all tricky, since in the end GH decides which workflo runs on a runner.

By adding a label to the workflow starting with ghr-ec2- and followed by the instance type a runenr for the required instance type is caled (only if the teature is enabled).

For example: ghr-ec2-m5.xlarge

Limitiation

• No support for pool (since not scaled by eventts)

Status

Early draft, just a POC, no tests, no docs, requires rerfactoing.

Todo

• Decide if this should enter the main line? If yes
• Refactor feature config to an object, containing enable and prefix
• Add docs including limitations
• Add unit tests
• Adjust an example, enable feature. Ephemeral case with job retry.
• Adjust logging