This reverts commit 0345b40a.

null = this lookup returned nothing last time
undefined = no cached result found

Co-authored-by: Yura Beznos <yury.beznos@ocado.com>
Co-authored-by: Jamie Magee <JamieMagee@users.noreply.github.com>
Co-Authored-By: Michael Kriese <michael.kriese@visualon.de>
Co-Authored-By: Rhys Arkins <rhys@arkins.net>

* refactor(github): Remove old Github platform wrappers

* Refactor 'util/cache/run' imports

* Fix pod http client

* Fix test

* refactor(pod): Split request functions

Co-authored-by: Michael Kriese <michael.kriese@visualon.de>
Co-authored-by: Rhys Arkins <rhys@arkins.net>

* chore(deps): update dependency prettier to v2

* Run prettier-fix

Co-authored-by: Renovate Bot <bot@renovateapp.com>
Co-authored-by: Jamie Magee <jamie.magee@gmail.com>

Ref #5555

A follow-up to #4246 which was insufficient.

The code to get a list of releases was not using the RENOVATE_ENDPOINT when the npm modules it was fetching releases for had it's git repository on github enterprise.

Closes #3079 

Closes #2529

This should fix the problem with fetching changelogs when using GHE.

Include body, message and stack with every error if present

Closes #2473

Adds the library `linkify-markdown` to actively linkify urls, issues and usernames so that they can then be linked to the renovatebot redirector for github.

This PR follows up and fixes #1968

The previous PR didn't behave correctly as it was expecting Github Enterprise to ALWAYS been configured and that the github.com token was available in the `GITHUB_COM_TOKEN` env variable.
But for non GHE project `GITHUB_COM_TOKEN` is not defined and github.com token is available at the `GITHUB_TOKEN` env variable instead.

This updated PR fix this issue and avoid further problems by prioritising `github.com` over GHE.
Now the code is NOOP if no `GITHUB_ENDPOINT` is configured.

If it's configured, instead, now the codes assumes that, by DEFAULT, a dependency is hosted on `github.com` so it removes `GITHUB_ENDPOINT` and use `GITHUB_COM_TOKEN` as Github token immediately.
They are restored only if needed, when a dependency is hosted on the provided GithubEnterprise.

This reverts commit f2fb2e6b.