Make helm charts consistent with how fields in spec are handled. (agent only)

[naemono]

related: #8184
related: #8192

Details of suggested change

This is the follow-up to #8192, where we are making the eck-agent helm chart consistent in how it handles values that end up within spec, and making it backwards compatible.

Implementation Note

1. The way this is implemented makes the previous behavior (having .spec.field in the values take precedence over just field in the values.
2. Mixing these 2 forms of values (some in spec in the values file, some not in spec) likely has unpredictable behavior. (for instance setting spec.http.something, and also setting http.somethingElse)

[naemono]

Sorry for delays merging this, I was doing some additional testing manually, and have noticed a bit of an issue I believe with default values. I'll update with more information.

[naemono]

Sorry for delays merging this, I was doing some additional testing manually, and have noticed a bit of an issue I believe with default values. I'll update with more information.

This change right here: ebaf618#diff-300fb79f6e3cf107546b30ff8193e64ec1bbf8a52dbe5b5a86fd3dd4bdb83384R111-R116 was causing failures in the fleet-server chart, when using the eck-stack parent chart, and it wasn't caught in our tests and I was wondering why, as there was a test for it. I caught this in some manual testing. This change 6bbdc4f fixes that. @thbkrkr I'd really like for you to give this another look when you can please.

[thbkrkr]

Good catch, still LGTM.

I guess we should do the same for suites declared in deploy/eck-stack/charts/eck-beats/templates/tests/beats-metricbeat-example_test.yaml in #8248.

Not related to this PR, I took another look to values in examples and we could remove the spec field for eck-kibana in:

• deploy/eck-stack/examples/agent/fleet-agents.yaml
• deploy/eck-stack/values.yaml