Three test cases that cover the regression scenarios introduced
by the helm#31644 nil preservation fix:

- subchart default nils should be cleaned up
when parent doesn't set those keys (helm#31919)
- user-supplied null should erase subchart defaults (helm#31919)
- subchart default nil should not shadow global values via pluck (helm#31971)

Tests are expected to fail until the regression is fixed.

Signed-off-by: Johannes Lohmer <jojo.dev@lohmer.com>

Regression test for the Bitnami common.secrets.key issue.

Signed-off-by: Johannes Lohmer <jojo.dev@lohmer.com>

Only user-supplied nils should survive coalescing. Chart-default nils
defaults, not just user overrides. This caused:
- %!s(<nil>) in templates using Bitnami common.secrets.key (helm#31919)
- pluck fallbacks returning nil instead of falling through to globals
  (helm#31971)

Fixes helm#31919
Fixes helm#31971

Signed-off-by: Johannes Lohmer <jojo.dev@lohmer.com>

…rt maps

Signed-off-by: Johannes Lohmer <jojo.dev@lohmer.com>

Signed-off-by: Evans Mungai <mbuevans@gmail.com>