pw_string: redo pw::string::Length

Moves and renames the existing pw::string::Length to
pw::string::internal::ClampedLength. Instead two new helpers are added:
1) pw::string::NullTerminatedLength(...) which returns the length IFF
   the string is null terminated.
2) pw::string::ClampedCString(...) which returns a string_view of
   the clamped string. This is considered safer compared to strnlen_s
   and the existing internal::ClampedLength implementation, since
   sting_view does not require null termination.

Change-Id: Ie6486df13b205332633f3970109ca97f578e6993
Requires: pigweed-internal:12460
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/43463
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_fuzzer/BUILD.gn b/pw_fuzzer/BUILD.gn
index 1359db4..91cbd08 100644
--- a/pw_fuzzer/BUILD.gn
+++ b/pw_fuzzer/BUILD.gn
@@ -80,7 +80,10 @@
 # Sample fuzzer
 pw_fuzzer("toy_fuzzer") {
   sources = [ "examples/toy_fuzzer.cc" ]
-  deps = [ "$dir_pw_string" ]
+  deps = [
+    "$dir_pw_result",
+    "$dir_pw_string",
+  ]
 }
 
 pw_test_group("tests") {