tests: optimize test-copytrace-heuristics.t test-copytrace-heuristics.t tests the heuristics algorithm of copytracing. The test has a pattern of making a server repo first and then cloning into a local repo for each test to have public and draft commits. This is done because if we have all draft commits and we have very less commits, heuristics will fallback to full copytracing as that will be fast. To avoid creating the server repo, we set the commit limit to -1 so that everytime we perform the heuristics algorithm even when having full drafts and tweak the config setting when we need to test the ability to fallback to full copytracing. This optimizes this test by 3 seconds. Before: real 0m41.503s user 0m36.068s sys 0m3.900s After: real 0m38.826s user 0m33.884s sys 0m3.396s Differential Revision: https://phab.mercurial-scm.org/D991