validateForm does not validate textarea or select inputs

[shadyvb]

​validateForm only looks for <input /> elements and ignores select and textarea fields.

Steps to reproduce:

• Add a select or textarea input to term edit page/form, add 'form-required' class to their wrappers
• Leave the new field(s) empty
• Click the submit button

Expected behavior:

• Form is not submitted, because required fields are not filled out

Actual result:

• Form validation passes and form is submitted

Recommended change:

• Change input:visible to :input:visible so it covers select and textarea as well.

[lukecavanagh]

@shadyvb

Patch applies cleanly without any errors.

[swissspidy]

In 40634:

Administration: Ensure validateForm also validates other input fields.

With this change, textareas and select inputs will be checked as well.

Props shadyvb.
Fixes #37540.