Feature: #80154 - Retrieve session data in TS

See forge#80154


As the session API has been modified, it is no longer possible to access session data from TypoScript by accessing the formerly public property of the fe_user with:

page.10 = TEXT
page.10.data = TSFE:fe_user|sesData|myext|mydata

This is being replaced by a more direct way, which allows for the same functionality:

page.10 = TEXT
page.10.data = session:myext|mydata