Extend teleTAN to 10 characters + input validation (#252)

* Change teleTAN from 7 to 10 characters

# Conflicts:
#	Corona-Warn-App/src/main/res/values/dimens.xml

* adjust TAN input to updated design

# Conflicts:
#	Corona-Warn-App/src/main/res/values/dimens.xml

* move TAN to upper case centrally

* styling of filled/empty TAN input spaces

* replace gradient at TAN entry with solid shape

* fix TAN input dash style

* add teleTAN input validation

* ensure valid characters are entered
* block further input if character is invalid
* mark invalid characters accordingly
* show error message if character is invalid
* calculate checksum
* show error and prevent the user from clicking „next“ if checksum is invalid

* code formatting

* Add include to TAN fragment

* Update teleTAN entry info text

* remove code smells

* Change detection of valid characters in TAN to whitelist

* add tests for TanHelper

* add tests for SubmissionTanViewModel

Co-authored-by: Jakob Möller <jakob.moeller@sap.com>