riscv: add rvv support

[Ag-Cu]

Summary

This pull request introduces support for the RISC-V Vector Extension (RVV) with 128-bit vector size in the sonic-cpp library.

Key Changes

CMake Configuration:

Added a new build option ENABLE_RVV_128 to enable RVV support. Updated set_arch_flags.cmake to include RVV-specific compile options.

RVV-Specific Implementations:

Added RVV-specific architecture files under include/sonic/internal/arch/rvv-128/. Implemented various SIMD operations for RVV, including string processing, integer conversion, and JSON quoting.

Test Results

[----------] Global test environment tear-down
[==========] 175 tests from 25 test suites ran. (43717 ms total)
[  PASSED  ] 175 tests.