Added bit_stream_reader, bit_stream_writer + other updates

Added etl::bit_stream_writer
Added etl::bit_stream_reader
Deprecated etl::bit_stream
Added callback option to etl::byte_stream_writer
Added error exceptions to byte_stream_writer
Added ETL_NODISCARD to etl::delegate create and is_valid functions
Added etl::visit support to etl::variant
Refactored C++17 message_packet
Refactored etl::atomic implementations to allow non-(integrals/pointers/bool)
Refactors etl::vector and etl::deque resize() to take const reference parameter
Renamed ETL_ALWAYS_ASSERT to ETL_ASSERT_FAIL
Removed duplicate void_t definition
Removed duplicate etl::declvar definition
Renamed cumulative_moving_average to pseudo_windowed_moving_average to more accurately reflect its algorithm.
Changed etl::debounce internal state names to avoid clashes with Arduino macros.