Make `erlangCookie` and `cookieAuthSecret` specifiable in `extraSecret`

[JustScreaMy]

What this PR does / why we need it:

This PR fixes an issue where a user attempting to use their own secret with extraSecretName and disabling createAdminSecret encounters an error during deployment. The error occurs because the chart expects cookieAuthSecret and erlangCookie to exist, but the secrets are not found.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• [x] Chart Version bumped
• [ ] e2e tests pass
• [x] Variables are documented in the README.md
• [x] NEWS.md updated

[JustScreaMy]

I have tried running E2E tests locally, but I always end up with a Error: failed linting and installing charts: failed identifying merge base: must be in a git repository