[RISCV] Codegen support for XCVbi extension (#89719)

spec:
https://github.com/openhwgroup/cv32e40p/blob/master/docs/source/instruction_set_extensions.rst#immediate-branching-operations

Contributors: @CharKeaney, @jeremybennett, @lewis-revill,
@NandniJamnadas,
@PaoloS02, @simonpcook, @xingmingjie, @realqhc, @PhilippvK,@melonedo