* chore: move as_byte_span() to new shell/common/mac_util.h
this way it can be used by multiple mm files
* fix: -Wunsafe-buffer-usage warnings in UNNotificationResponseToNSDictionary
* refactor: use base::HexEncode() instead of rolling our own
* fixup! chore: move as_byte_span() to new shell/common/mac_util.h
* fixup! chore: move as_byte_span() to new shell/common/mac_util.h
fix: move mac_util to the right place in filenames.gni
