ctb: Fix Holocene upgrade script

[sebastianst]

Description

A couple of fixes to the Holocene upgrade script.

• bumped the contracts release to use to rc.2.
• removed '' from sed -i '' invocations - this is a MacOS quirk, but doesn't work in a Linux Docker env.
• deployment script is only run if deployments aren't present yet.
• deploy-config.json was made a parameter to just run.
• output folder is an optional second parameter to just run. Defaults to output/.
• scripts are copied from the checked out repo, not the contracts revision of the monorepo, allowing to use newer scripts (and possibly modify them locally).
• improved documentation in README.

[mslipper]

The issue breaking the merge queue here has been fixed - should be good to merge once the above convo is resolved.