Fix secure credential loading for nested team-config profiles

[ATorrise]

What It Does
When testing #408 i found that the way i structured my config was returning 401s
ie:

mainframe ->
  -> properties
       -> host
  -> profiles
       -> zosmf ->
            -> properties
                 -> port
            -> secure
                 -> user
                 -> password

found that __load_secure_properties looked for zosmf as a direct key of the mainframe profile but zosmf actually lives one level deeper, under the profiles key.

the fix to config_file.py handles however many levels a config nests

test_custom_file_and_custom_profile_loading_with_nested_profile user/password values came from a plaintext override in nested.zowe.config.user.json, not from the vault. So apparently no test ever exercised __load_secure_properties for a profile nested more than one level deep with secure fields on the child! Added a new test (test_nested_profile_with_secure_properties_on_child) that pulls creds from the mocked vault
How to Test
change your config to match this level of nesting when testing. verify that you get 401s on main and you can run system tests on this branch :)
Review Checklist
I certify that I have:

• updated the changelog
• manually tested my changes
• added/updated automated unit/integration tests
• created/ran system tests (provide build number if applicable)
• followed the contribution guidelines

Additional Comments

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.20%. Comparing base (3329790) to head (8c1bed4).

Files with missing lines	Patch %	Lines
src/core/zowe/core_for_zowe_sdk/config_file.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #411      +/-   ##
==========================================
+ Coverage   84.82%   85.20%   +0.38%     
==========================================
  Files          49       49              
  Lines        3011     3002       -9     
==========================================
+ Hits         2554     2558       +4     
+ Misses        457      444      -13     

Flag	Coverage Δ
unittests	85.20% <75.00%> (+0.38%)	⬆️

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[zFernand0]

LGTM! 😋

Very good catch! 🙏

Here is a quick before and after of this fix:

Before

{'rejectUnauthorized': False, 'host': 'lpar.1', 'port': 1234}
HTTP Request has failed with status code 401. 

After

{'rejectUnauthorized': False, 'host': 'lpar.1', 'port': 1234, 'user': 'dummy', 'password': 'dummy'}
HTTP Request has failed with status code 401. 

I got the 401 because dummy:dummy is not valid on my system

---

With proper creds:

{'rejectUnauthorized': False, 'host': 'lpar.1', 'port': 1234, 'user': 'REALUSER', 'password': 'PASSWORD'}
//* //FERNAN00 JOB (IZUACCT),FERNANDO,CLASS=B,MSGCLASS=X,TYPRUN=HOLD
...

[traeok]

I noticed that even with these changes, the failure is never raised from check_missing_props, which is likely why @zFernand0 was seeing a 401 rather than an explicit error. I'd consider it out of scope for this PR, but worth a follow-up issue.

Aside from that, I left a suggestion around the modified code in an attempt to de-duplicate logic.

dismissing self-review

[zFernand0]

The missing coverage is just on a line that I fixed a typo 😢

[traeok]

I thoroughly reviewed c9f60d1 in addition to the PR as a whole, no concerns here and code changes LGTM 😋
The only outstanding concern is that patch is at 75% instead of the target 80%, but since its not a required stage for Python SDK I'm not going to hold up the PR over it.

Thanks Fernando!