contrib/asv.conf.json

check-config: syntax to allow inconsistent config values

The ignore regular expression has been updated to detect
"inconsistent config." If present, we track which configs have
that set and we suppress the conflicting defaults error for those
options.

I also added named groups to the regexp to aid readability.

A comment was added to profiling.py to make a desired inconsistent
value error go away.

{
    "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"
}