Replace std::basic_string_view<uint8_t> with std::span

In newer versions of libc++, std::char_traits<T> is no longer defined
for non-character types, and a result, std::basic_string_view<uint8_t>
is also no longer defined. See
https://discourse.llvm.org/t/deprecating-std-string-t-for-non-character-t/66779.

Bug: 175635923
Test: libkeymint_remote_prov_support_test
Change-Id: Ic373e0a3c081b996d4c81a9783103ae6406833f7