RISC-V: WARL checks for misa CSR

Context

Adds WARL field checks for misa CSR. Relevant section: 3.1.1 privileged spec.

Extensions chosen: A + C + D + F + I + M + S + U

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misa CSR encoding:

MXL encoding:

Extensions encoding:

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR