[apriltags] Use map as internal data model (#4577)

This leaves the file format as a list, but internally will transform the collection of tags into a map on de/serialization. The serialization will probably happen once on startup, but the tag lookup can happen 100s of times a second. This honestly probably doesn't make too much of a performance hit since N is small, but this is a simple O(n) -> O(1) change for lookups.

wpilibc/src/main/native/include/frc/apriltag/AprilTagFieldLayout.h

@@ -6,6 +6,7 @@
 
 #include <optional>
 #include <string_view>
+#include <unordered_map>
 #include <vector>
 
 #include <units/length.h>
@@ -101,7 +102,7 @@ class WPILIB_DLLEXPORT AprilTagFieldLayout {
   bool operator!=(const AprilTagFieldLayout& other) const;
 
  private:
-  std::vector<AprilTag> m_apriltags;
+  std::unordered_map<int, AprilTag> m_apriltags;
   units::meter_t m_fieldLength;
   units::meter_t m_fieldWidth;
   bool m_mirror = false;