riscv64: add disassembler support for Zawrs

[newborn22]

Add disassembly support and tests for Zawrs extension on RISCV64.

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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[gopherbot]

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[gopherbot]

This PR (HEAD: 8dd4828) has been imported to Gerrit for code review.

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