Use string_view to compute custom string hash C++17 supports std::hash<string_view>, which can be used to compute a hash for the custom sh::TString class. This eliminates the dependency on smhasher. Bug: b/260426695 Change-Id: I2f4044fea4e44396a5d798436ec02da22a37bed7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4066987 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Nicolas Capens <nicolascapens@google.com>