[JITLink][RISCV] Support GOT/PLT relocations

This patch add the R_RISCV_GOT_HI20 and R_RISCV_CALL_PLT relocation support. And the basic got/plt was implemented. Because of riscv32 and riscv64 has different pointer size, the got entry size and instructions of plt entry is different. This patch is the basic support, the optimization pass at preFixup stage has not been implemented.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D107688