Feature: #83734 - Add support for current page in config.cache

Description

When using the TypoScript property config.cache, it is possible to define a configuration that affects all pages via:

config.cache.all = fe_users:2

However such configurations always depend on a precise page where to look up records. A common scenario is to have records stored in each page itself. Thus, the syntax with the keyword "current" is now possible:

config.cache.all = fe_users:current

where current is dynamically replaced by the current Page ID.

Impact

When using current inside the config.cache TypoScript property, it is now replaced with the current Page ID.