This PR closes [Issue
#13482](https://github.com/nushell/nushell/issues/13482)
# Description
This PR tend to make all math function to be constant.
# User-Facing Changes
The math commands now can be used as constant methods.
### Some Example
```
> const MODE = [3 3 9 12 12 15] | math mode
> $MODE
╭───┬────╮
│ 0 │ 3 │
│ 1 │ 12 │
╰───┴────╯
> const LOG = [16 8 4] | math log 2
> $LOG
╭───┬──────╮
│ 0 │ 4.00 │
│ 1 │ 3.00 │
│ 2 │ 2.00 │
╰───┴──────╯
> const VAR = [1 3 5] | math variance
> $VAR
2.6666666666666665
```
# Tests + Formatting
Tests are added for all of the math command to test there constant
behavior.
I mostly focused on the actual user experience, not the correctness of
the methods and algorithms.
# After Submitting
I think this change don't require any additional documentation. Feel
free to correct me in this topic please.
