Refactor TruthTable.apply and add factory method for Espresso (backport #2612) (#2620)

* Refactor TruthTable.apply and add factory method for Espresso (#2612)

Improves performance of creating TruthTables by processing entire BitPats
rather than individual bits. New TruthTable factory method enables
constructing TruthTables with semantics of OR-ing output BitPats together
rather than erroring when multiple terms have the same input BitPat.
This alternative factory method matches semantics for the output format
of Espresso.

Co-authored-by: Megan Wachs <megan@sifive.com>
Co-authored-by: Jack Koenig <koenig@sifive.com>
(cherry picked from commit 231f14e7

)

# Conflicts:
#	src/main/scala/chisel3/util/BitPat.scala

* Resolve backport conflicts

Co-authored-by: Aditya Naik <91489422+adkian-sifive@users.noreply.github.com>