Add warning for `rescue_from Exception` and `rescue_from StandardError`

[ci skip]
Always assume strings with non-numeric characters change numeric types

We previously only did this if the old value was zero, to make sure
numericality validations run and failed if the user gave 'wibble' as the
value, which would be type cast to 0. However, numericality validations
will fail if there are any non-numeric characters in the string, so 5 ->
'5wibble' should also be marked as changed.
Merge pull request #15895 from sgrif/sg-numeric-changes

Always assume strings with non-numeric characters change numeric types
Doc pass for `Type::Value` [ci skip]
Merge pull request #15828 from yuki24/add-warning-about-rescue-from-exception

Add warning section for `rescue_from Exception` in Guides
Dont swallow errors when bad alias_method