Add processor duration metric

[andborja]

Description

Add duration metric to processors.

Testing

Unit tests added.

Documentation

Implements issue Processor duration metric #13231.

Basic documentation generated by mdatagen.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: andborja / name: Andres Borja (475f6b4, d25590d)

[atoulme]

@andborja please make sure you review and sign the CLA.

[andborja]

@andborja please make sure you review and sign the CLA.

Thanks @atoulme. I just created a ticket for it.

[axw]

LGTM, would like to see the test simplified though. Thanks for adding this!

[axw]

Suggested change

	// Regardless of how many logs are ingested, emit just one
	mockAggregate := func(_ context.Context, _ plog.Logs) (plog.Logs, error) {
	ld := plog.NewLogs()
	ld.ResourceLogs().AppendEmpty().ScopeLogs().AppendEmpty().LogRecords().AppendEmpty()
	return ld, nil
	}
	incomingLogs := plog.NewLogs()
	incomingLogRecords := incomingLogs.ResourceLogs().AppendEmpty().ScopeLogs().AppendEmpty().LogRecords()
	// Add 3 records to the incoming
	incomingLogRecords.AppendEmpty()
	incomingLogRecords.AppendEmpty()
	incomingLogRecords.AppendEmpty()
	tel := componenttest.NewTelemetry()
	lp, err := NewLogs(context.Background(), newSettings(tel), &testLogsCfg, consumertest.NewNop(), mockAggregate)
	require.NoError(t, err)
	assert.NoError(t, lp.Start(context.Background(), componenttest.NewNopHost()))
	assert.NoError(t, lp.ConsumeLogs(context.Background(), incomingLogs))
	nop := func(_ context.Context, ld plog.Logs) (plog.Logs, error) {
	return ld, nil
	}
	tel := componenttest.NewTelemetry()
	lp, err := NewLogs(context.Background(), newSettings(tel), &testLogsCfg, consumertest.NewNop(), nop)
	require.NoError(t, err)
	assert.NoError(t, lp.Start(context.Background(), componenttest.NewNopHost()))
	assert.NoError(t, lp.ConsumeLogs(context.Background(), plog.NewLogs()))

Much of that setup is irrelevant to the test, and is distracting from what's really being tested. Same goes for metrics & traces.