feat: add support for custom base url filtering

[louis-murray]

Background

When cumulusCI goes to execute a command against a specific org, it generates some config of the org. Part of the config is a lightningBaseUrl. The lightningBaseUrl composition tries to standardize the base url by setting the base url to *.lightning.force.com.

There are a few edge cases where the instance we're interacting with is using a wholly custom url format so a .lightning.force.com url isn't going to be accurate. In those cases, the .lightning.force.com url will cause robot actions to fail when trying to interact with the instance.

Resolution

In this PR, I introduce two env vars:

• SF_CUSTOM_URL_RE - The shape of the url to match
• SF_CUSTOM_URL_BASE - How to set the base url when the above matches

The config inflation will check if an org's url matches these env vars before defaulting to the .lightning.force.com base url.

[salesforce-cla]

Thanks for the contribution! It looks like @louis-murray is an internal user so signing the CLA is not required. However, we need to confirm this.