[Forms] Add a feature to disable forms

[tudoramariei]

Is your feature request related to a problem? Please describe.

Forms might only need to be open for a while, and with their links spread over many pages, it can be challenging to locate and remove each one.
In such cases, you might randomly receive submissions because someone found an orphaned link.

Describe the solution you'd like

Create a mechanism to disable a form and block users from submitting more information.

Control:

• If Store submissions and Send submissions by email are turned off, the form should be disabled.
• The feature could also be controlled through a switch in the admin panel like the ones for Store submissions or Send submissions by email, but it should be separate to avoid confusion.
• It would be helpful to allow for an expiration date & time for a form's availability (i.e., to enable people to register for an event)

Views:

• Depending on the available features, a minimal implementation would block the user from submitting their responses.
• Additionally, gray out the fields to ensure the user doesn't enter data to discover the form is disabled.

Additional context

We thought about this feature after some forms were still receiving submissions, although we had removed the links from all (known) places.