Use std::string_view and fmtlib across all libraries (#3402)

- Twine, StringRef, Format, and NativeFormatting have been removed
- Logging now uses fmtlib style formatting
- Nearly all uses of wpi::outs/errs have been replaced with fmt::print() or
std::puts()/std::fputs() (for unformatted strings).
- A wpi/fmt/raw_ostream.h header has been added to enable
fmt::print() with wpi::raw_ostream

wpilibc/src/main/native/include/frc/smartdashboard/SendableBuilder.h

@@ -96,7 +96,7 @@ class SendableBuilder {
    */
   virtual void AddStringProperty(
       std::string_view key, std::function<std::string()> getter,
-      std::function<void(wpi::StringRef)> setter) = 0;
+      std::function<void(std::string_view)> setter) = 0;
 
   /**
    * Add a boolean array property.
@@ -140,7 +140,7 @@ class SendableBuilder {
    */
   virtual void AddRawProperty(std::string_view key,
                               std::function<std::string()> getter,
-                              std::function<void(wpi::StringRef)> setter) = 0;
+                              std::function<void(std::string_view)> setter) = 0;
 
   /**
    * Add a NetworkTableValue property.
@@ -162,8 +162,8 @@ class SendableBuilder {
    */
   virtual void AddSmallStringProperty(
       std::string_view key,
-      std::function<wpi::StringRef(wpi::SmallVectorImpl<char>& buf)> getter,
-      std::function<void(wpi::StringRef)> setter) = 0;
+      std::function<std::string_view(wpi::SmallVectorImpl<char>& buf)> getter,
+      std::function<void(std::string_view)> setter) = 0;
 
   /**
    * Add a boolean array property (SmallVector form).
@@ -213,8 +213,8 @@ class SendableBuilder {
    */
   virtual void AddSmallRawProperty(
       std::string_view key,
-      std::function<wpi::StringRef(wpi::SmallVectorImpl<char>& buf)> getter,
-      std::function<void(wpi::StringRef)> setter) = 0;
+      std::function<std::string_view(wpi::SmallVectorImpl<char>& buf)> getter,
+      std::function<void(std::string_view)> setter) = 0;
 
   /**
    * Get the network table.