[FEATURE] Add FluidEmail option to EXT:form EmailFinisher

EXT:form, the last system extension not using FluidEmail
was extended for the corresponing integration. To allow
extension authors to smoothly test and upgrade, the old
StandaloneView functionality remains for now.

As there is no change to the present behaviour the switch
can be done without further actions required - if using the
default templates currently.

To migrate custom templates to FluidEmail, the template files
must be changed from the {@format}.html syntax to appropriate
names with the correct format extension like `.html` and `.txt`.
Furthermore the `templateName` option must be set with the new name.

Two fields are introduced to configure FluidEmail in the finishers:

- `useFluidEmail`: Enables sending the mails via FluidEmail
- `title`: Used for the title section of the default template

Resolves: #90728
Releases: master, 10.4
Change-Id: I378b733554ba734ad4eb6dff60e1da48ca03c972
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65699


Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>