P24 adds the official branch tests

P24 widens P23 from twenty-five official tests to thirty-one by adding the branch group.

Command:

make -C projects/24_rv32i_branch_tests/test

Result: PASS

Summary: PASS=31 FAIL=0 NOT RUN=0

The newly passing tests are I-beq-00.S, I-bne-00.S, I-blt-00.S, I-bltu-00.S, I-bge-00.S, and I-bgeu-00.S.

The remaining official RV32I/I gap is memory access: loads and stores.