feat: add extraManifests to opentelemetry-collector helm chart

[SBejga]

This PR is adding the possibility to specify extra manifests to deploy with the opentelemetry-collector.

e.g. if you are managing secrets with external secrets operator or onepassword-operator you need to specify an additional manifest, that will create a secret for you, that you can use with the opentelemetry-collector.

Example using onepassword-operator

extraManifests:
- apiVersion: onepassword.com/v1
  kind: OnePasswordItem
  metadata:
    name: example-onepassword-secret
  spec:
    itemPath: vaults/Examples/items/example

I have seen and used this in several projects by using a helm parameter extraManifests and want to add this to the opentelemetry-collector helm chart.

[linux-foundation-easycla]

• ✅login: SBejga / (71cfdcd)

The committers listed above are authorized under a signed CLA.

[TylerHelmuth]

Fixes #1361. @open-telemetry/helm-approvers I'd like your opinion before moving forward with this idea.