This PR improves the `evalInt?` function, which is used to evaluate
configuration parameters from the `ToInt` type class. This PR also adds
a new `evalNat?` function for handling the `IsCharP` type class, and
introduces a configuration option:
```
grind (exp := <num>)
```
This option controls the maximum exponent size considered during
expression evaluation. Previously, `evalInt?` used `whnf`, which could
run out of stack space when reducing terms such as `2^1024`.
closes#9427
7d2a7dba81