[pdata] Prevent `RemoveIf` memory leak by erasing truncated values in slices

[mx-psi]

In the RemoveIf methods we can erase truncated values in slices explicitly to prevent a memory leak. This issue is meant to track the prior TODO on the code originally added in #2998:

opentelemetry-collector/pdata/internal/cmd/pdatagen/internal/base_slices.go

Lines 115 to 116 in 7f56849

	// TODO: Prevent memory leak by erasing truncated values.
	*es.orig = (*es.orig)[:newLen]

[dmitryax]

This is resolved by #13522