fix(helm): pass arrays via per-element --set-string args

[danilovid]

Helm's --set treats ["a","b"] as a literal string, so generating
--set 'admission-controller.ignoredNamespaces=["a","b"]' failed chart
schema validation with Expected: array, given: string.

Refactor buildHelmArgs to recurse into slice/array elements and emit
one --set-string 'name[i]=value' per element. The same path also
correctly handles arrays of structs (e.g. notifier.overwriteEnv),
which the previous JSON-marshaled form already mis-encoded.