[JS] Implement JsInterop support for Java Records.

This change adds support for using JsInterop annotations on Java Records and their components in J2CL.

- Record component fields are implicitly treated as JsProperties.
- Record component accessors inherit their JsInterop configuration from the components and are restricted from having explicit annotations to avoid conflicts.
- Native records are disallowed as they don't have a meaningful representation in this context.
- `@JsOptional` is disallowed on record components. Maybe will be later allowed on explicit canonical constructors.

More details are covered in docs/design/records-jsinterop.md

In particular this CL only includes changes and tests for Java frontend. Kotlin-Java interop on Record with jsinterop is currently blocked due the problem where private fields are hidden. I will include that with a patch to kotlinc in a later iteration.

PiperOrigin-RevId: 910517409

Author: gkdn

java/jsinterop/annotations/JsMethod.java

@@ -23,7 +23,7 @@
 
 /**
  * JsMethod marks a method that will be directly translated into a JavaScript method preserving its
- * name.
+ * name. They are not allowed on record component accessors.
  *
  * <p>Note: In JavaScript, instance members are defined on the prototype and class members are
  * defined on the constructor function of the type.

java/jsinterop/annotations/JsType.java

@@ -40,10 +40,15 @@
  * <p>Name collisions must be avoided by providing custom names (e.g. {@link JsProperty#name}) or by
  * ignoring members using {@link JsIgnore}.
  *
+ * <p>When applied to a Java record, all public record components are implicitly exposed as
+ * read-only properties. The canonical constructor is also implicitly exposed as a {@link
+ * JsConstructor}. Non-canonical constructors cannot be exposed so they should be marked with {@link
+ * JsIgnore}.
+ *
  * <p>If the JsType is marked as "native" via {@link #isNative}, then the type is considered a stub
  * for an existing class that is available in native JavaScript. Unlike non-native JsTypes, all
  * members are considered {@link JsProperty}/{@link JsMethod}/{@link JsConstructor} unless they are
- * explicitly marked with {@link JsOverlay}.
+ * explicitly marked with {@link JsOverlay}. Records cannot be marked as native.
  *
  * <p>For native interfaces with no particular JavaScript type associated with them (e.g. structural
  * types) it is recommended to use {@code namespace = JsPackage.GLOBAL} and {@code name = '?'}.