A follow-up to #4246 which was insufficient.

chore(deps): update node.js to v12.9.0

Fixes #4359

As described on Slack, the regex versioner is currently causing bad PRs
such as [this](https://github.com/TheKevJames/experiments/pull/8) since
it can not properly track the current version. By parsing the `range`
values with the same logic as the other version strings, eveverything
should match up properly.

The regex versioner supports arbitrary, user-defined versioning
methods; it provides building blocks in the way of interacting capture
groups within a user-defined regex which can be combined to support
arbitrary use-cases.

Uses a new `versionConfig` option to configure this scheme -- this
feature is enabled dynamically for any new versioner which includes the
optional `configure?(new_config: string)` interface. Warns if used with
an invalid scheme.

There are cases where the first page of results is not representative of the entire branch's status, so we need to follow all pages in the result.

Closes #4340

Closes #4317

Closes #4317