[TASK] Introduce TCA cache layer

Implement a new cache logic for TCA tables located in an extensions
Configuration/TCA directory. The filenames must be named like the
table name and must return arrays.
This way, TCA of a table is defined and loaded by just adding
a file at the correct position and returning the array result.

The bootstrap now finds those files and constructs the 'base' TCA
from it, together with a cache layer for next run. This simple
cache layer is used in frontend and backend transparently.
ext_tables.php should not define $GLOBALS['TCA']['some_table']
anymore, but can still overload the base TCA of foreign tables
with own columns and settings using the ExtensionManagementUtility
methods.

When moving TCA from ext_tables to Configuration/TCA, it is
important to not add any code logic inside those files, for
example date function calls are not good since the result is cached.

Location example: ext:sys_note/Configuration/TCA/sys_note.php
defines table TCA of $GLOBALS['TCA']['sys_note'].