[fieldImages] Move Java fields to edu.wpi.first.fields (#6694)

Doesn't make sense in edu.wpi.fields, and resources are already in
edu.wpi.first.fields
This will require changes in Shuffleboard and Pathweaver

fieldImages/src/test/java/edu/wpi/first/fields/LoadConfigTest.java

@@ -0,0 +1,19 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.fields;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
+
+class LoadConfigTest {
+  @ParameterizedTest
+  @EnumSource(Fields.class)
+  void testLoad(Fields field) {
+    FieldConfig config = Assertions.assertDoesNotThrow(() -> FieldConfig.loadField(field));
+
+    Assertions.assertNotNull(config.getImageUrl());
+  }
+}