Add no. prefix

[SeeminglyScience]

The no. prefix (EMCA §III.2.2) seems to be excluded from both SRE.OpCodes and SRM.ILOpCodes. I'll need to find out if it's actually supported and why it was excluded.

[SeeminglyScience]

Some background on the prefix in dotnet/runtime#10112. I may still implement or just leave it to _emit (#25).

[SeeminglyScience]

For now I'm going to leave this to _emit, e.g.

il { [int]([object]) } {
    ldarg.0
    _emit(0xFE, 0x19, 0x01)
    unbox { [int] }
    ldobj { [int] }
    ret
}

[abelbraaksma]

You may want to check this as well: dotnet/runtime#35491.