Issue #19087: Improve bytearray allocation in order to allow cheap popping of data at the front (slice deletion).

_frozen_importlib and source.

This mostly affected the encodebytes and decodebytes function
(which are used by base64_codec)

Also added a test to ensure all bytes-bytes codecs can handle
memoryview input and tests for handling of multidimensional
and non-bytes format input in the modern base64 API.