libjpegrecoverymap: add support for multi-threading

Generate recovery map and apply recovery map process are now split
across threads.

Bug: 261877699
Test: push files from tests/data to /sdcard/Documents and then \
 atest libjpegdecoder_test libjpegencoder_test libjpegrecoverymap_test

Change-Id: I05ccdb170bfe1c2647bbbcd3662c97350b41b3f1