[ perf ] Use alternative better GC on chez

[buzden]

Description

At least @edwinb and I are using this collect-request-handler for at least more than half of a year and we were discussing at the last weekly Idris chat that it's time to make all users happy being able to use this.

In case you doubt, you can try this GC handler and play with this patcher which replaces only the handler in the given *.ss file (recompiling the *.so one) or installed app name (using pack).

Should this change go in the CHANGELOG?

• If this is a fix, user-facing change, a compiler change, or a new paper
  implementation, I have updated CHANGELOG_NEXT.md (and potentially also
  CONTRIBUTORS.md).