Trace Redaction - Convert task rename from primitive to filter

Filter task rename events was one of the first primitives implemented.
Since then, ScrubFtraceEvents has been changed as wrapper for ftrace
event filters.

This changes the scrub task-rename primitive to a filter. This is
important for two reasons:

  1. The iteration logic in the primitive is shared and less likely
     to contain errors.

  2. Re-serialization is minimized.

Bug: 318576499
Change-Id: I3a50c760fd0ffcc97ff3a4a8d17aa79e9a09c397