Read previousVersions for bincompat checking from a file (backport #3202) (#3207)

* Read previousVersions for bincompat checking from a file (#3202)

This makes it much easier to automate checking new versions as they are
released.

---------

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
(cherry picked from commit 2c6028b0

)

# Conflicts:
#	build.sbt

* Enable binary compatibility checking against 3.6.0

---------

Co-authored-by: Jack Koenig <koenig@sifive.com>