* Tone down the performance of some runners from 8cpu+ down to 4cpu+
* Improve and document caching on PX4 builds with an improved ccache key strategy
* Review and document artifact upload logic for binaries uploaded to S3 and github
releases
* Future Improvement, introduce runners configuration file so we can
control more precesily which instances are allocated.
Signed-off-by: Ramon Roche <mrpollo@gmail.com>
