fix(nlu): trim entity occurences on change

[franklevasseur]

fixes DEV-1217
fixes botpress/v12#1215

[linear]

DEV-1217 [BUG] Entity creation with leading and trailing white spaces (botpress/botpress botpress/v12#1215)

Describe the bug
It is possible to create the same entity using leading and trailing white spaces, they are all treated as the same one, but later causes issue in comparisons ex.: (if entity === 'one')

To Reproduce
Steps to reproduce the behavior:

1. create a list entity
2. add "one" -> no space
3. add " one" -> space before
4. add " one " -> space before and after
5. add "one " - space after
6. add "one" -> here we get a "duplicate error"

Expected behavior
Trimmed entities

Screenshots

Environment (please complete the following information):

• 12.16.3

Additional context
Add any other context about the problem here.

[rob-gordon]

It may be easier to compare against trimmed strings in isUniqueInEntity and then update untrimmed strings once on save, rather then on each onChange event - but N/B

Looks good!