Add freeze config option for autoupdate command

This commit adds a new 'freeze' option to the CONFIG_SCHEMA, allowing users
to set 'freeze: true' in their pre-commit configuration file.

The intend are two effects, when setting `freeze: True`:
* Enables freeze automatically when running `pre-commit autoupdate` (no
  need then anymore to specify --freeze).
* Enables https://pre-commit.ci/ to freeze hooks as part of update PRs.

pre_commit/commands/autoupdate.py

@@ -176,6 +176,8 @@ def autoupdate(
         if repo['repo'] not in {LOCAL, META}
     ]
 
+    freeze = freeze or load_config(config_file)['freeze']
+
     rev_infos: list[RevInfo | None] = [None] * len(config_repos)
     jobs = jobs or xargs.cpu_count()  # 0 => number of cpus
     jobs = min(jobs, len(repos) or len(config_repos))  # max 1-per-thread