This commit implements all the arm64 instruction encodings necessary for our JIT compiler and replaces the golang-asm assembler with our handmade assembler on arm64 platform. Notably, this allows us to do concurrent compilations. This closes #233 combined with #406. Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io> Co-authored-by: Adrian Cole <adrian@tetrate.io>