Rename the `blocklyToolboxDiv` CSS class to `blocklyToolbox`

[BeksOmega]

Rename any references to blocklyToolboxDiv to blocklyToolbox.

This change should be made against the rc/v12.0.0 branch. This should be marked as a breaking change.

To work on this issue, comment below asking to be assigned.

[Venki1402]

@BeksOmega I would like to work on this issue. Can you assign it to me?

[BeksOmega]

Go for it @Venki1402 =)

[Venki1402]

@BeksOmega Thanks!

[ruthwikchikoti]

hey @Venki1402 i want to work on this issue !!!

[Venki1402]

@BeksOmega could you pls review this PR?

[shivam1234100]

Hey @BeksOmega can I work on this?

[BeksOmega]

Sure @shivam1234100 =) Let me know if you have any questions!