feat(driver): BitScrambler support

This adds an assembler for the BitScrambler assembly language,
plus unit tests for it. It also adds the loopback driver,
which can do BitScrambler operations on memory-to-memory
transfers. Documentation is also included.

tools/test_bsasm/testcases/opcode_src.bsasm

@@ -0,0 +1,12 @@
+
+cfg lut_width_bits 32
+
+main:
+	if 0 main
+	ifn 32 main
+	if l0 main
+	ifn a0 main
+	if o0 main
+	ifn h main
+	if l main
+	ifn o31 main