Removed SkSL::StringFragment in favor of string_view

This CL preserves the "StringFragment" name as an alias for
string_view to reduce the impact. The StringFragment alias
will be removed in a followup CL.

Change-Id: I89209bc626b0be0d0190823b6217f4c83cafe1bc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/416736
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
44 files changed