Add support for Zcmt extension

[nadime15]

Hi everyone,

This pull request adds support for the Zcmt extension.

I’ve also included some simple tests, which can be found here.

• Reading from the jump table vector requires Execute permission and supports both little and big endian formats. The current RISC-V Sail model only allows little-endian access, but I will add big-endian support after Big endianness Support added #751 is merged.
• Check if Smstateen is implemented, requires state enable bit 2 in the appropriate stateen0 CSR. Will be added after Add Smstateen/Ssstateen extension regs #694 is merged.

One observation: at some point, it might make sense to introduce a more general interface for load and store. Since the Zcmp (#730) extension also requires these operations, a shared implementation could help reduce code duplication.

[nadime15]

Hi @Timmmm, thanks for the suggestions! I've incorporated them and left some comments about a few small issues I ran into.

[github-actions]

Test Results

400 tests  ±0   400 ✅ ±0   1m 47s ⏱️ -2s
  1 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 15b5029. ± Comparison against base commit 97b7ed5.

♻️ This comment has been updated with latest results.