Add back and expose source category for events source

[maimaisie]

Description

Since the events data doesn't go through metadata enrichment plugin currently, the source category for events source is just the default http after we removed static source category for all sources in #349.

This PR adds it back just for events source and expose it in values.yaml file. Since after Sam's breaking change, all events configuration fields go under events I am adding it here in case this goes out in a minor release before the major one to avoid one more rename that customer needs to do when we do make the major release.

Testing performed

• ci/build.sh
• Redeploy fluentd and fluentd-events pods
• Confirm events, logs, and metrics are coming in
• Ran helm template to verify overwriting the field

[rvmiller89]

should we move eventCollectionEnabled under this, maybe as:

events:
  collectionEnabled: true
  sourceCategory: ""

?

[maimaisie]

this will be changed after #349

[rvmiller89]

I'm confused, #349 is already merged

[maimaisie]

oh sorry wrong one, it is #330, specifically this change

[rvmiller89]

Great, thanks for confirming

[rvmiller89]

why not use what we had below to set the default sourceCategory: "%{namespace}/%{pod_name}"

[maimaisie]

I am using the source category we had for events before for consistency. Also what would pod name be in this case? For logs it's the name of the pod that logs are coming from I assume, but events are not only about pods. We can't use the pod name of the events pod itself either, since we don't know the pod name at the time of the source creation in TF