Merge RISC-V LLD Code-Size Optimizations into Main
This merge integrates the RISC-V LLD code-size optimization changes into the main branch.
The main changes include:
- Weighted GP selection and writable data section reordering;
- Function-level InputSection splitting;
- Independent garbage collection for split functions;
- Safe identical code folding for split functions;
- Link-time relaxation from JAL to C.J/C.JAL;
- Cleanup of related configuration options, tests, and documentation.
The relevant tests have been completed successfully. Program correctness is preserved, and the optimized version achieves a reduction in the final executable size compared with the original version.