[TASK] Deprecate various TSFE methods

A lot of functionality has been migrated from
TypoScriptFrontendController into middlewares
- functionality that has now no direct influence
in the so-called controller of the frontend (TSFE)
anymore. The respective methods are never called
anymore from TYPO3 Core, and extensions that
bootstrap their own frontend should ensure that
the respective Middlewares are boot up and called,
e.g. via custom stacks or just by setting up
the "frontend" middleware stack.

The following methods are now deprecated:
- connectToDB()
- checkAlternativeIdMethods()
- initializeBackendUser()
- handleDataSubmission()
- setCSS()
- convPOSTCharset()

Additionally, there are some methods in TSFE
which have been marked as "internal" but had the
PHP visibility "public", which were now
migrated to "protected".

- getPageAndRootline()
- checkRootlineForIncludeSection()
- setSysPageWhereClause()
- checkAndSetAlias()
- getHash()
- getLockHash()
- setUrlIdToken()

Resolves: #84965
Releases: master
Change-Id: Ia8e29268189179061c09a204bb7275d231fea0dc
Reviewed-on: https://review.typo3.org/56916


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Cristian Buja <cristian.buja@intera.it>
Tested-by: Cristian Buja <cristian.buja@intera.it>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>