Allow tuning of logs batching behavior

[cbandy]

Checklist:

• Have you added an explanation of what your changes do and why you'd like them to be included?
• Have you updated or added documentation for the change, as applicable?
• Have you tested your changes on all related environments with successful results, as applicable?
  • Have you added automated tests?

Type of Changes:

• New feature

What is the current behavior (link to any open issues here)?

Batches of logs are exported every 200ms.

What is the new behavior (if this is a feature change)?

Users can configure the size and frequency of batches via the API. Documentation on each field explains what they do and why each is useful.

Other Information:

Issue: PGO-2176

[benjaminjb]

Are we going to use this Processor? Seems like we could ditch it (I'm 10 files in)

[cbandy]

It's still used in some metrics pipelines. 🤔 Worth a review later.

[benjaminjb]

We don't use this var outside of the if feature.Enabled block, do we? And technically only use it once?

[benjaminjb]

Do we need both kubebuilder defaults (when do those run, on admission?) and a default func?

[cbandy]

This is called by collector.NewConfig even when the section hasn't been filled out in the spec. IIUC, k8s doesn't fill out defaults inside missing optional fields.

Like,

---
# input from user:
instrumentation: {} # `batches` is missing and optional, no default; k8s does not add it

---
# input from user:
instrumentation: 
  batches: null  # missing; stays null; nothing happens with defaults inside

---
# input from user:
instrumentation:
  batches: {}    # present; some fields inside have defaults

# k8s sets and stores defaults:
instrumentation:
  batches:
    maxDelay: 200ms
    minRecords: 8192

---
# similarly, input:
instrumentation:
  batches:
    maxDelay: 1min

# k8s sets and stores defaults:
instrumentation:
  batches:
    maxDelay: 1m
    minRecords: 8192

📝 Default() used to satisfy some interface in controller-runtime for webhooks, but that style didn't work well for all webhooks. [Migrating]

[benjaminjb]

No blockers (and happy to combine those pgadmin pipelines in my pgadmin PR)