[TASK] Remove default files (DirectoryIndex)

Few default files are included in the directories typo3 and install
in case the server does not have the necessary DirectoryIndex.

Those can be removed since php is needed and DirectoryIndex
will include index.php in standard setup.

Change-Id: I5b5660b8f74242bd0924c89e105dee6dbb278fb8
Fixes: #45786
Releases: 6.1
Reviewed-on: https://review.typo3.org/18456
Reviewed-by: Wouter Wolters
Reviewed-by: Oliver Klee
Reviewed-by: Soren Malling
Tested-by: Soren Malling
Reviewed-by: Michael Stucki
Tested-by: Michael Stucki
[BUGFIX] Make backend user global available early

The global must be available very early, because methods below
might trigger code which relies on it. In particular the workspace
overlay of the rootline which is done in certain cases.

Fixes: #45625
Releases: 6.0, 6.1
Change-Id: I035f27e11cd56fc284442b66ad8357060f76e52c
Reviewed-on: https://review.typo3.org/18420
Reviewed-by: Mattias Nilsson
Reviewed-by: Oliver Klee
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
[TASK] Remove not necessary require_once in LiveSearchDataProvider

Change-Id: I2027184626850ff7dc13221b30db9077406ce9ca
Resolves: #45865
Releases: 6.1
Reviewed-on: https://review.typo3.org/18486
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
[FEATURE] Refactor TCA handling

This patch refactors TCA handling especially in the frontend to
a new codebase, making it more easy to work with, removing
developer headaches, without significant performance impact:

* In FE, full TCA is always loaded and cached after first call
to a core cache disk. ext_tables are not executed on every call.
* In BE, intermediate TCA is cached, rendering the dynamicConfigFile
setting useless. The destinction between 'ctrl' and 'columns' is
gone.
* TCA files should now be located at
ext:extensionname/Configuration/TCA/tablename.php' and should return
an array with the TCA for the table specified by the filename. On
first access, those files are read and cached. 'ctrl' sections from
ext_tables.php can be removed completly.
* TSFE->includeTCA(), TSFE->getCompressedTCarray() and
GeneralUtility:loadTca() are obsolete and deprecated.
* Extensions not using the new TCA load scheme have a compatibility
layer in ext_tables.php to resolve 'dynamicConfigFile' directly after
a specific extensions ext_tables.php file was loaded, so the next one
can already manipulate it with ExtensionManagementUtility methods.
* t3lib/stddb is gone, all files are merged to core.

Resolves: #45767
Releases: 6.1
Change-Id: I50ebe00c80b9b58ded0586637c85e0f495a63dad
Reviewed-on: https://review.typo3.org/18452
Tested-by: Soren Malling
Tested-by: Mattias Nilsson
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-by: Felix Kopp
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Merge remote-tracking branch 'origin/master' into masterGithub