Updating the project RISC-V asm and analysis capabilities

[moste00]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository.
• I made sure to follow the project's coding style.
• I've documented every RZ_API function and struct this PR changes.
• I've added tests that prove my changes are effective (required for changes to RZ_API).
• I've updated the Rizin book with the relevant information (if needed).
• I've used AI tools to generate fully or partially these code changes and I'm sure the changes are not copyrighted by somebody else.

Detailed description

As per #5275, this PR builds on the refactored Capstone RISCV plugin in capstone-engine/capstone#2756 and propagates the change to Rizin, adding lots of Rizin-specific capbilities.

(1- AI Disclosure) I use Gemini CLI in the context of the codebase, mostly or almost exclusively for read-only type of usage: as an intelligent search engine to navigate and query the codebase, I almost always reject edit requests by it. I also use Claude Web for general questions, routine text editing, and other context-free tasks.

(2- Diff Density) I expect most of the changes to be concentrated heavily in the analysis-riscv-cs.c file, because this file wasn't updated in 5 years and is in heavy need for updates to take advantage of the new Capstone module, however the first state of this PR mostly focuses on minimal changes to get it to compile and pass tests, most of the diff is instead build file glue and tests modification.

(3- Temp Changes) Some changes are temporary and won't survive the merging of this PR, for example a legacy GNU plugin is kept as-is to reduce diff noise but just renamed to riscv.gnu so it's not the default (and the RISCV plugin is renamed to riscv from riscv.cs), and some build system logic is added so that we can build with a local development version of Capstone instead of a published release.

Test plan

With the exception of relevant tests under db/esil, all old tests are relevant and will be kept and made to pass. New tests must be added from a variety of source to ensure the new capabilities. This section is evolving as more tests are added.

NOTE, to any reviewer running locally: Change the local path in subprojects/capstone-capstone-riscv-updated.wrap to a Capstone archive containing the RISCV updates.

Closing issues

** Depedents **

Depends-on: rizinorg/rizin-testbins#223
Depends-on: #5666
Depends-on: capstone-engine/capstone#2756

[wargio]

to be reverted (leave this comment here till the branch is merged)

[notxvilka]

For arithmetic functions you need to provide all necessary op-> fields and operations, so that analysis engine knows enough to work even without ESIL. Take a look how it's done in analysis_mips_cs.c. Setting op->src and op->dst where appropriate, as well as op->ptr and op->refptr, op->jump, op->stackop, op->stackptr, etc

[moste00]

Understood, op->stack* are set sepearetly after the switch by set_stack_effect though

[notxvilka]

@moste00 don't forget about this please

[notxvilka]

Please don't forget to remove the old GNU plugin. I recommend squashing it into two commits:

• one is to remove old RISC-V GNU plugins
• second is to add new plugins

[Rot127]

I just recognized that this whole effort means the RISCV features in Capstone are not well enough defined I think. Rizin is the first tool using the new CS plugin and implements a work around for the features? This is not a good sign.

@moste00 I didn't recognized this when we talked in Mattermost, but I think we should at least consider using alternatives.

cc @notxvilka @wargio