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.

wpilibc/src/main/native/cpp/smartdashboard/MechanismLigament2d.cpp

@@ -12,7 +12,7 @@ MechanismLigament2d::MechanismLigament2d(std::string_view name, double length,
                                          units::degree_t angle,
                                          double lineWeight,
                                          const frc::Color8Bit& color)
-    : MechanismObject2d(name),
+    : MechanismObject2d{name},
       m_length{length},
       m_angle{angle.value()},
       m_weight{lineWeight} {