Use stricter C++ type conversions (#4357)

Now, implicit narrowing conversions are only used with wpi::Now(). This
also fixes clang-tidy warnings about C-style casts. For example:
```
== clang-tidy /__w/allwpilib/allwpilib/wpilibNewCommands/src/main/native/include/frc2/command/SwerveControllerCommand.inc ==
/__w/allwpilib/allwpilib/wpilibNewCommands/src/main/native/include/frc2/command/SwerveControllerCommand.inc:95:18: warning: C-style casts are discouraged; use static_cast/const_cast/reinterpret_cast [google-readability-casting]
  auto curTime = units::second_t(m_timer.Get());
                 ^
```
In that case at least, the cast was removed entirely since Get() already
returns a units::second_t.

wpilibcExamples/src/main/cpp/commands/parallelcommandgroup/ReplaceMeParallelCommandGroup.cpp

@@ -9,5 +9,5 @@
 // https://docs.wpilib.org/en/stable/docs/software/commandbased/convenience-features.html
 ReplaceMeParallelCommandGroup::ReplaceMeParallelCommandGroup() {
   // Add your commands here, e.g.
-  // AddCommands(FooCommand(), BarCommand());
+  // AddCommands(FooCommand{}, BarCommand{});
 }