Add feature-gate to delete original time field from parsed container logs

[ChrsMark]

Description:

This PR adds support for removing the original time attribute/field from the parsed log record as it was suggested at #33389.
Users should use the Timestamp field which holds the parsed time.

This patch introduces this change behind a feature flag called filelog.container.removeOriginalTimeField which is disabled by default following the feature lifecycle.

Link to tracking Issue: #33389

Testing:

1. Added unit-test
2. Run with ./bin/otelcontribcol_linux_amd64 --config container_config.yaml --feature-gates=filelog.container.removeOriginalTimeField and verify the output:

2024-07-08T14:26:50.936+0300	info	LogsExporter	{"kind": "exporter", "data_type": "logs", "name": "debug", "resource logs": 1, "log records": 2}
2024-07-08T14:26:50.936+0300	info	ResourceLog #0
Resource SchemaURL: 
Resource attributes:
     -> k8s.namespace.name: Str(some)
     -> k8s.pod.name: Str(kube-controller-kind-control-plane)
     -> k8s.container.restart_count: Str(1)
     -> k8s.pod.uid: Str(49cc7c1fd3702c40b2686ea7486091d6)
     -> k8s.container.name: Str(kube-controller)
ScopeLogs #0
ScopeLogs SchemaURL: 
InstrumentationScope  
LogRecord #0
ObservedTimestamp: 2024-07-08 11:26:50.836517638 +0000 UTC
Timestamp: 2029-03-30 08:31:20.545192187 +0000 UTC
SeverityText: 
SeverityNumber: Unspecified(0)
Body: Str(INFO: log line here)
Attributes:
     -> logtag: Str(F)
     -> log.file.path: Str(/var/log/pods/some_kube-controller-kind-control-plane_49cc7c1fd3702c40b2686ea7486091d6/kube-controller/1.log)
     -> log.iostream: Str(stdout)
Trace ID: 
Span ID: 
Flags: 0

Documentation: Added.

[djaglowski]

A feature gate seems a little excessive here because the operator is very new and the information being deleted is available in a more helpful form elsewhere on the log. I'm fine with leaving it if you prefer but also ok with simplifying.

[ChrsMark]

I'm in two minds about the feature gate :). My only concern is about potentially breaking the Helm preset which switched to the container operator as well. @TylerHelmuth's any thoughts on this since this could affect the Helm chart users?

If we agree on this I'm happy to remove the feature gate and land it with the direct deletion.

[rogercoll]

LGTM! Just a small comment

[rogercoll]

Shouldn't we log this message when not using the feature gate instead? That way would make the user that is not using the gate, aware of the future removal.

Suggested change

	if removeOriginalTimeField.IsEnabled() {
	if !removeOriginalTimeField.IsEnabled() {

[ChrsMark]

Good catch, that was the intention since the gate will be initially in StageAlpha.
Thank's for catching this!

[andrzej-stencel]

It's probably more meaningful for users if we set the component to receiver/filelog? Especially that the feature gate has filelog in its name.