Refactor from env vars to defaults.yaml

[1000TurquoisePogs]

This PR moves the server from depending heavily on a confusing list of environment variable decision making for configuration, to instead having a configuration based almost entirely on YAML files, and includes its own defaults.yaml file to refer to and build upon.

This will support both dev and prod. In prod, the defaults file will be used in combination with the user's yaml file, allowing that to be brief but yet make visible how you can customize the server further.

In dev, the defaults.yaml will be copied to ~/.zowe/zowe.yaml if it doesnt exist, which will give you a starting point for customization. From then on, the server would by default load both that file and the defaults.yaml file.

The defaults.yaml file is found within defaults/serverConfig/defaults.yaml
It uses configmgr-like templating in the format of ${{ }} with some tweaks:

• you can use os. and process. calls because it's getting executed in nodejs, not configmgr.
• the server doesnt do schema validation, because zwe does, but that means dev has no schema validation.
• the functions within templates seem not to be able to be arrow functions, thus you will see the pattern of function a() {thing}; a() a bit, to accomplish the same thing.

This PR addresses Issue: zowe/zlux#914

This PR depends upon the following PRs: zowe/zlux-server-framework#473

Type of change

Please delete options that are not relevant.

• Refactor the code

PR Checklist

Please delete options that are not relevant.

• If the changes in this PR are meant for the next release / mainline, this PR targets the "staging" branch.
• My code follows the style guidelines of this project (see: Contributing guideline)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes
• Relevant update to CHANGELOG.md
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works, or describe a test method below

Testing

This PR should [ass existing automation for dev and prod. use it as you would normal zowe. additionally, you can find tests of yaml files within https://github.com/zowe/zlux-server-framework/pull/473

[1000TurquoisePogs]

alert automation that we'll be breaking them here.