Description of problem:

Length validation fails to throw when the machine pool name exceeds 15 characters. Currently the length validation error thrown to user when the machine pool name size exceed more than 30 characters. This is wrong because when user try to add the machine pool name exceeds 15 characters, the dialog will throw inline error 

Steps to reproduce:

1. Install ROSA hypershift cluster via CLI .
2. Launch OCM UI staging.
3. Once installation is successful, Open the newly installed ROSA hypershift cluster.
4. Navigate to machine pools tab and click on the "Add machine pool" button.
5. Keep the name of the machine pool to a string that exceed more than 30 characters.
6. Keep the name of the machine pool to a string that exceed more than 15 characters but less than 30 characters
7. Try to add machine pool and view the behavior.

Actual results:
In  Step 5, It throws the length validation error as it is exceeding 30 characters.
In  Step 7, Although the length of the machine pool name below 30 characters, the creation of machine pool failed as there is a limit for node/machine pool to 15 characters.

Expected results:
During the length validation on machine pool name field should restrict with 15 characters and it should throw validation error to user when it exceeds the size of characters > 15.
There should not be any check for 30 characters and this is wrong.