Add support for Zilsd and Zcmlsd extension

[lavanyajagan]

Description

Adding Support for Zilsd and Zcmlsd Extensions presented here:

Related Issues

The related PRs

• riscv-config support for the extension merged in dev PR
• riscv-isa-sim support for the extension available in master : commit id
• SAIL PR
• riscv-ctg PR
• riscv-isac PR
• Sample test env

Update to/for Ratified/Unratified Extensions or to framework

• [ ] Ratified
• [x] Unratified
• [ ] Framework

List Extensions

The unratified spec document: https://github.com/riscv/riscv-zilsd/blob/main/zilsd.adoc

Reference Model Used

• [x] SAIL
• [x] Spike
• [ ] Other - < SPECIFY HERE >

Mandatory Checklist:

• [ ] Make sure to have created a suitable entry in the CHANGELOG.md under [WIP-DEV] section.