7) Seq instructions

Created by: abukharmeh

Adds initial implementation of the sequencer and sequenced instructions (tbljal, pushpop and double move) Adds BEQI and BNEI Fix assertions for Zext/ Sext Fix March ID @davideschiavone Can you have a look at this one please, thank you !

NOTE: This PR finishes implementing the features of Zce v0.5 https://github.com/riscv/riscv-code-size-reduction/releases/tag/V0.50.1-TOOLCHAIN-DEV , in next sets of PRs, will tune the design and move to v0.7