Don't force public variables to use Hungarian notation (#8774)

People generally have expressed a dislike for the Hungarian notation
used in member variables, especially in examples/templates, and our
styleguide shouldn't be forced on downstream consumers, so this removes
all Hungarian notation from the examples/templates.

There are _some_ benefits to Hungarian for private member variables
(like knowing what's a member vs. local in a PR review) so we'll keep
private member variables the same for now, but public variables should
no longer use Hungarian notation, since it looks much worse. A new PMD
XPath rule has been added to accomplish this goal. Some other
non-compliant variables were fixed for the new rule.

styleguide/spotbugs-exclude.xml

@@ -150,6 +150,10 @@
     <Bug pattern="UUF_UNUSED_PUBLIC_OR_PROTECTED_FIELD" />
     <Class name="org.wpilib.epilogue.EpilogueConfiguration" />
   </Match>
+  <Match>
+    <Bug pattern="URF_UNREAD_FIELD" />
+    <Class name="org.wpilib.driverstation.internal.DriverStationBackend$HALJoystickAxesRaw" />
+  </Match>
   <Match>
     <!-- PMD will skip variables named `ignore`, but spotbugs isn't as smart -->
     <Bug pattern="DLS_DEAD_LOCAL_STORE" />