[!!!][TASK] Make sys_template not workspace aware

The patch makes table "sys_template" no longer
obey workspaces: The workspace related fields
are gone and the overlay calls removed. An upgrade
wizard sets all existing workspace overlay rows
to deleted.

There are quite a few reasons to do this:

* Workspaces is about content: pages, tt_content and
  attached inline relations are content. All that
  is typically editable by editors. But TypoScript
  templates are system configuration: Templates and
  the Template module are admin-only, editors can't
  and shouldn't fiddle here. When content depends on a
  sys_template change, editors can't publish this in
  one go. Having sys_template table workspace aware is
  a conceptual flaw from this point of view since it
  creates a hard dependency to admin actions when
  publishing content.

* Preparing sys_template changes in a workspace is
  not a good development workflow: More and more
  TypoScript is delivered by file includes under VCS
  to be easily manageable and deployable. Spreading
  TypoScript using sys_template records in the page
  tree is becoming old fashioned and contracts
  this good practice.

* Workspace aware sys_template record usages are an
  seldom edge case: Most situations can be handled
  by preparing TypoScript in live already. Typical
  use cases are additional CSS files, which can be
  prepared in live by admins already using different
  selectors or TypoScript conditions and similar.

* The workspace implementation of sys_template records
  was at least partially broken: Neither the Backend
  Template module nor the frontend worked with it
  flawlessly, especially when multiple sys_template
  records on one page were handled.

* Removing workspace awareness for sys_template records
  reduces complexity and gives us a do-able path to
  improve performance on a query level in further v12
  core development, especially in Frontend full-cached
  page scenarios and for instances not using workspaces
  at all.

Change-Id: Id5fdd5c8f9c91ae134bea7506f0b31bf47b28fee
Resolves: #98480
Releases: main
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75918


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>