feat(java): add read/write filters for Java field usages (#569)

Find Usages mixed reads and writes of a Java field, including Lombok getter and setter calls, because jdtls has no read/write classification in its references. The usages popup and Find window now have Read and Write toggles. Read-write accesses stay visible in either mode and unclassified results are kept.

Classification comes from a jdtls extension in `plugins/java-usages`, embedded as a jar and installed beside the other bundles. The checked-in jar was rebuilt from source with ECJ and matches byte for byte. Any extension failure falls back to standard references, so a jdtls upgrade can lose the filter but not Find Usages; rebuilding the jar on an upgrade is manual and described in the plugin README. Older installed jars are removed. Other languages keep their plain result count.

Co-authored-by: NingYuanLin <[email protected]>

plugins/java-usages/plugin.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<plugin>
+  <extension point="org.eclipse.jdt.ls.core.delegateCommandHandler">
+    <delegateCommandHandler class="ai.openidea.usages.UsagesCommand">
+      <command id="openidea.java.usages"/>
+    </delegateCommandHandler>
+  </extension>
+</plugin>