feat: JWT Preflight Check

[hrishikesh-nalawade]

Description

A Java utility that verifies connectivity to the z/OSMF JWK endpoint before/after starting the Zowe API Mediation Layer. This tool helps diagnose configuration issues early such as incorrect hostnames, unreachable ports, missing certificates, or misconfigured z/OSMF by performing a lightweight HTTP(S) call to the z/OSMF JWK endpoint at /jwt/ibm/api/zOSMFBuilder/jwk

Linked to #4526

Type of change

• feat: New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• PR title conforms to commit message guideline ## Commit Message Structure Guideline
• I have commented my code, particularly in hard-to-understand areas. In JS I did provide JSDoc
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• The java tests in the area I was working on leverage @nested annotations
• Any dependent changes have been merged and published in downstream modules