feat(secrets): Core crate to expose Rust modules as library

[traeok]

What It Does

This PR implements the following changes for the Secrets SDK:

• Exposes the Rust core logic as a crate named secrets_core so that other languages can leverage it to create bindings
  • See PR 222 on the Python SDK 😋
• Adjusts the Rust crate so it can be imported by other Rust-powered Zowe projects (such as the daemon)
• Adds basic unit tests to the secrets_core crate

How to Test

Build the Secrets SDK package using npm run build - compilation should succeed.

Review Checklist
I certify that I have:

• tested my changes
• added/updated automated tests
• updated the changelog
• followed the contribution guidelines

Additional Comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d775c37) 91.06% compared to head (970a95d) 91.06%.
Report is 1 commits behind head on master.

❗ Current head 970a95d differs from pull request most recent head bc046f3. Consider uploading reports for the commit bc046f3 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1844   +/-   ##
=======================================
  Coverage   91.06%   91.06%           
=======================================
  Files         636      636           
  Lines       18709    18709           
  Branches     3898     3898           
=======================================
  Hits        17037    17037           
  Misses       1671     1671           
  Partials        1        1           

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[t1m0thyj]

I feel awkward approving this PR since I pushed a commit, but changes LGTM 👍

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[zFernand0]

I didn't run into any issues with the build.
LGTM! 😋

[zFernand0]

I believe we landed on no-changelog required for the secrets_core crate.

Note:

• The only other PR merged before this one was the Readme updates.

Merging and labeling as release-current