Pad RISC-V RVC instructions like Thumb2

[fuad1502]

We're introducing RVC instructions to RISC-V JIT in dotnet/runtime: dotnet/runtime#117408

With that PR and this PR, output of R2RDump tool for the following C# method:

publicstaticlongFunAdd(longa,longb){returna+b;}

is as follows:

long Program.FunAdd(long, long)Handle: 0x06000002Rid: 2EntryPointRuntimeFunctionId: 1Number of RuntimeFunctions: 1long Program.FunAdd(long, long)Id: 1StartAddress: 0x00010BD0Size: 34 bytesUnwindRVA: 0x0001091CDebug Info Bounds: Native Offset: 0x0, Prolog, Source Types: StackEmpty Native Offset: 0x10, IL Offset: 0x0000, Source Types: StackEmpty Native Offset: 0x12, Epilog, Source Types: StackEmpty Variable Locations: Variable Number: 0 Start Offset: 0x0 End Offset: 0x10 Loc Type: VLT_REG Register: A0 Variable Number: 1 Start Offset: 0x0 End Offset: 0x10 Loc Type: VLT_REG Register: A110bd0: 130101 ff addi sp,sp,-1610bd4: 23308100 sd s0,0(sp)10bd8: 23341100 sd ra,8(sp)10bdc: 13040100 mv s0,sp10be0: 2e 95add a0, a0, a1 ;; RVC instruction10be2: 83308100 ld ra,8(sp)10be6: 03340100 ld s0,0(sp)10bea: 13010101 addi sp,sp,1610bee: 67800000ret

[fuad1502]

Hi @am11 can you help me review this PR or assign an appropriate reviewer with write access for this PR? 🙏 The related PR in dotnet/runtime (dotnet/runtime#117408) is already merged in 👍

[am11]

@jakobbotsch, @EgorBo, PTAL. LGTM! :)