[format.arg] Changed declartion of basic_format_arg::handle's ctor in class to match change in itemdecl.

…th lvalues

…seful

[flat.set.defn][flat.multiset.defn] Clean up indentation for consistency.

…ameter

Fixes NB GB 081, GB 082 (C++23 CD).

…st charT[N], charT>

… expected<U, G>&) should take precedence over expected(U&&) with operator bool

…strained

Fixes NB GB 121 (C++23 CD).

Fixes NB CA 076 (C++23 CD).

…l-formed

…ition

…r std::expected

…eams objects