[SimplifyCFG] Delete the unnecessary range check for small mask operation

When the small mask value little than 64, we can eliminate the checking
for upper limit of the range by enlarge the lookup table size to the maximum
index value. (Then the final table size grows to the next pow2 value)
```
bool f(unsigned x) {
    switch (x % 8) {
        case 0: return 1;
        case 1: return 0;
        case 2: return 0;
        case 3: return 1;
        case 4: return 1;
        case 5: return 0;
        case 6: return 1;

        // This would remove the range check: case 7: return 0;
    }
    return 0;
}
```
Use WouldFitInRegister instead of fitsInLegalInteger to support
more result type beside bool.

Fixes https://github.com/llvm/llvm-project/issues/65120
Reviewed By: zmodem, nikic, RKSimon