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 <57001533+NingYuanLin@users.noreply.github.com>

plugins/java-usages/tests/ReadWrite.java

@@ -0,0 +1,24 @@
+import lombok.*;
+import lombok.experimental.Accessors;
+interface Counter { int getCount(); void setCount(int value); }
+@Data class Bean implements Counter { public int count; public Bean next; public int[] items; }
+class Child extends Bean {}
+@Data @Accessors(fluent=true, chain=true) class Fluent { public int score; }
+class Use {
+ void uses(Bean b, Child c, Counter i, Fluent f) {
+  int read = b.count; // read
+  b.count = 1; // write
+  b.count += 2; // readWrite
+  b.count++; // readWrite
+  --b.count; // readWrite
+  b.setCount(b.getCount()); // setter write, getter read; nested invocation ranges
+  c.setCount(c.getCount()); // inherited
+  i.setCount(i.getCount()); // interface
+  java.util.function.IntSupplier ref = b::getCount; // unknown
+  java.util.function.IntConsumer writeRef = b::setCount; // unknown
+  f.score = f.score(); // field write, fluent read
+  f.score(f.score()); // fluent setter write, getter read
+  b.items[0] = 1; // reading array field, writing element
+  b.next.count = 2; // reading receiver field, writing count
+ }
+}