branchcache: rework the `filteredhash` logic to be more generic
We now have a more flexible `key_hashes` tuple. We duplicated various logic in
the V2 and V3 version of the cache as the goal is to start changing the logic
for V3 in the next few changesets.
{
"version": 1,
"project": "mercurial",
"project_url": "https://mercurial-scm.org/",
"repo": "..",
"branches": ["default", "stable"],
"environment_type": "virtualenv",
"show_commit_url": "https://www.mercurial-scm.org/repo/hg/rev/",
"benchmark_dir": "benchmarks",
"env_dir": "../.asv/env",
"results_dir": "../.asv/results",
"html_dir": "../.asv/html"
}