fix: Avoid casting settings before env var expansion

[WillDaSilva]

This fixes a regression in #7232. In that PR logic was added to cast settings within the setting store. This was needed because some settings were not retrieved through a settings service in order to avoid infinite regression (i.e. the get method in a setting service cannot generally call itself).

A consequence of those changes was that now we are casting setting values before env var expansion has occurred. To address the regression, this PR makes the casting logic from #7232 disabled by default, and it is only enabled when accessing settings from within the get methods of a setting service (where we cannot rely on the regular setting casting).

A cleaner approach would be preferable, but this should be sufficient to address the regression while preserving the bug fix that #7232 implemented.

Closes #7293

[netlify]

✅ Deploy Preview for meltano canceled.

Name	Link
🔨 Latest commit	17a08b1
🔍 Latest deploy log	https://app.netlify.com/sites/meltano/deploys/63e561e46ca92000088c44cd

[codecov]

Codecov Report

Merging #7294 (17a08b1) into main (11f948d) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #7294      +/-   ##
==========================================
- Coverage   89.57%   89.56%   -0.01%     
==========================================
  Files         288      288              
  Lines       21469    21479      +10     
  Branches     2373     2373              
==========================================
+ Hits        19230    19237       +7     
- Misses       1874     1875       +1     
- Partials      365      367       +2     

Impacted Files	Coverage Δ
src/meltano/core/settings_service.py	97.50% <100.00%> (ø)
src/meltano/core/settings_store.py	94.05% <100.00%> (-0.60%)	⬇️
...ests/meltano/core/test_project_settings_service.py	100.00% <100.00%> (ø)

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[WillDaSilva]

The new test may be is flaky: https://github.com/meltano/meltano/actions/runs/4131188538/jobs/7138602617

I have yet to reproduce a failure like this.

EDIT: The flaky test was fixed in 17a08b1