JIT: If-conversion costing rejects `(cond ? 1 << a : 0)` even on RISCV where this gets explicitly targeted

We have this optimization in if-conversion that turns `SELECT(cond, 1 << a, 0)` into `cond << a`. It only runs on RISCV:
https://github.com/dotnet/runtime/blob/b70c35ed8a2e7ae0d91de76f4f5d26c2e7d2c6cd/src/coreclr/jit/ifconversion.cpp#L721-L728

However our current cost-analysis always rejects such patterns. Example:
```cs
int Cond1Shift(bool cond, int a)
{
return cond ? (1 << a) : 0;
}
```
If we look at JitDump:
```md
***** BB03 [0002]
STMT00001 ( 0x005[E--] ... 0x00B )
N006 ( 11, 9) [000009] -----+----- * RETURN int $VN.Void
N005 ( 10, 8) [000008] -----+--R-- \--* LSH int $143
N004 ( 1, 2) [000004] -----+----- +--* CNS_INT int 1 $41
N003 ( 5, 5) [000007] -----+----- \--* AND int $142
N001 ( 3, 2) [000005] -----+----- +--* LCL_VAR int V01 arg1 u:1 (last use) $c0
N002 ( 1, 2) [000006] -----+----- \--* CNS_INT int 31 $44
Skipping if-conversion that will evaluate RHS unconditionally at costs 1,10
```

So the optimization above for RISCV is essentially dead code. We always bail out earlier which is probably not wanted.