Add support to localhost urls while debugging

[sergiolms]

Description

These changes will allow testing local development on APIs and backend services of gk-dev. With this, you can now set the following settings in settings.json (made up urls for the example):

{
	"gitkraken.env": "local",
	"gitkraken.url": {
		"api": "http://localhost:1314/api",
		"gkdev": {
			"base": "http://localhost:1314",
			"api": "http://localhost:1314/gkdev/api"
		}
	}
}

NOTE: URLs will only be applied when gitkraken.env is set to local. Also, the local environment has the same restrictions as dev and staging (only available if it's pre-release or debugging).

Checklist

• I have followed the guidelines in the Contributing document
• My changes follow the coding style of this project
• My changes build without any errors or warnings
• My changes have been formatted and linted
• My changes include any required corresponding changes to the documentation (including CHANGELOG.md and README.md)
• My changes have been rebased and squashed to the minimal number (typically 1) of relevant commits
• My changes have a descriptive commit message with a short title, including a Fixes $XXX - or Closes #XXX - prefix to auto-close the issue that your PR addresses

[axosoft-ramint]

I suggest instead of this.prereleaseOrDebugging, to allow the value local for gitkraken.env and then checking that here.

And if it is local and this url is not provided, we should throw because we don't want someone targeting prod and thinking they were on a local setup.

Same with the other cases.

[sergiolms]

I started with that local value for env, but if I do that and you only want to overwrite 1 URL, you still have to manually put the other ones because env won't tell you anymore if you're on dev, staging or prod. Which is totally okay if we want to do that and make the developer aware they have to manually set all URLs in config. In fact, my first commit does that, and I could retake it if we want to go down this path and throw instead of setting a default URL, as you said.

However, I found it unconvenient that you had to manually set all URLs if you wanted to overwrite just one, so I switched to a useLocal boolean that would "enable" the use of URLs, but again it seemed like setting an URL should be enough to specify that it should use it. With that, you would overwrite the desired URL, and leave all the rest up to env to decide where to point at.

Again, I'm totally up for both options so I appreciate the point of view