Convert string class names

Automated using git grep & sed.
Replace StringC classes with StringView classes.
Remove the CFX_ prefix and put string classes in fxcrt namespace.
Change AsStringC() to AsStringView().
Rename tests from TEST(fxcrt, *String*Foo) to TEST(*String*,
Foo).
Couple of tests needed to have their names regularlized.

BUG=pdfium:894

Change-Id: I7ca038685c8d803795f3ed02545124f7a224c83d
Reviewed-on: https://pdfium-review.googlesource.com/14151
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
diff --git a/testing/test_support.cpp b/testing/test_support.cpp
index 0ebb747..b32ec7d 100644
--- a/testing/test_support.cpp
+++ b/testing/test_support.cpp
@@ -105,8 +105,8 @@
 }
 
 std::string GetPlatformString(FPDF_WIDESTRING wstr) {
-  CFX_WideString wide_string =
-      CFX_WideString::FromUTF16LE(wstr, CFX_WideString::WStringLength(wstr));
+  WideString wide_string =
+      WideString::FromUTF16LE(wstr, WideString::WStringLength(wstr));
   return std::string(wide_string.UTF8Encode().c_str());
 }