add keyring support

[js665999]

adds ability to load certificates from keyrings on z/OS
new options:
-n, --keyring keyring name
-o, --keyring-owner keyring owner id
-l, --keyring-label keyring certificate label

keyring options are used when certificates are not loaded via -c and -k options

[NakulManchanda]

Mocha and Eslint both are reporting vulnerabilities on lodash - on their latest version - alternative use some other packages
Will be outside scope of this PR to find those alternative so considering disabling audit to merge this one.

We need to add tests for new options here:
https://github.com/zowe/explorer-ui-server/tree/staging/test/https-combos

we are failing one existing test:

1. test https combos
   using pfx-pass should return index.html when requesting /:

and then we can approve and merge,
i can add same.
thanks

[sonarcloud]

SonarCloud Quality Gate failed.

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

73.0% Coverage
0.0% Duplication

The version of Java (1.8.0_242) you have used to run this analysis is deprecated and we will stop accepting it from October 2020. Please update to at least Java 11.
Read more here

[NakulManchanda]

Refactored https Configuration and added test

[jackjia-ibm]

Overall looks good to me