tests: add more custom tests

chore: load gcd parameters from memory

chore: move inital sp to 1020

feat: store c results in memory addr 0

feat: make RAM word aligned, add byte_enable

Support sb, sh, lb, lh using byte enable
instead of non-word aligned reads and writes.

feat: add gcd program for testing

feat: add branches.c test

chore: remove gcc generated file

feat: add basic testing programs