Using ```estring_view``` instead of ```std::string_view``` for APIs, to avoid ABI inconsistency between C++ versions

We make extensive use of string_view for efficient handling of strings. And we use it in C++14 mode by cheating std library, and let it think we are in c++17 mode. This compiles OK, but leads to ABI inconsistency in binaries.

The issue names no files, tests, or entry points. Start by locating the public APIs that use string_view and comparing their C++14 and C++17 ABI behavior; done should mean the affected APIs use estring_view without ABI inconsistency between C++ versions.

Written by the indexing model from the issue text.