Revert "Prime cache for tone mappers in mediaserver"

This reverts commit d4fe6b13.

Reason for revert:
This CL was meant to pre-init the RenderEngine to save time
on the actual thumbnail extraction. But it is using more
memory after boot.

Since HDR clips are less common at present, we'll delay the
init to first use for now.

bug: b/147047966
test: atest android.media.cts.MediaMetadataRetrieverTest

Change-Id: I5b8799bbe2f4ae496e15b5ba699203223fe3013b