[build] Enable spotbugs (#3601)

Benign spotbugs warnings were suppressed, and all others were fixed. Bug
descriptions are documented here:
https://spotbugs.readthedocs.io/en/stable/bugDescriptions.html

Co-authored-by: Austin Shalit <austinshalit@gmail.com>

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

@@ -21,6 +21,7 @@ MechanismLigament2d::MechanismLigament2d(std::string_view name, double length,
 
 void MechanismLigament2d::UpdateEntries(
     std::shared_ptr<nt::NetworkTable> table) {
+  std::scoped_lock lock(m_mutex);
   table->GetEntry(".type").SetString("line");
 
   m_colorEntry = table->GetEntry("color");