Currently clang-format uses ContinuationIndent to indent the contents of a raw
string literal that is the last parameter of the function call. This is to
achieve formatting similar to trailing:
f(1, 2, R"pb( x: y)pb");
However this had the unfortunate consequence of producing format like this:
fffffff(1, 2, R"pb( a: b )pb");
This patch makes clang-format consider indenting a trailing raw string param
after a newline based off the start of the format delimiter, producing:
fffffff(1, 2, R"pb( a: b )pb");