[release-tools] Tool to find related commits

[release-tools] Tool to find related commits

usage: This tool analyzes the commit range between <of> and <until>. It finds commits which belong together e.g. Implement/Revert pairs and Implement/Port/Revert triples. All supplied hashes need to be from the same branch e.g. master.

Example for M42: ./search_related_commits.py --prettyprint --separator e0110920d6f98f0ba2ac0d680f635ae3f094a04e b856e8785933a2a9cd884ab8966fee0e7098927e b1c2a3495624a9776c7df865d972886f2d078c10

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/1098123002

Cr-Commit-Position: refs/heads/master@{#28197}