GWT recompilation does not occur if you modify a properties file located on a submodule

# Description:
When I modfiy a file included in a client module and when I reload the page through the browser I expect the GWT plugin automatically recompile it. However (at least in the case of messages and constants) this does not happen if the files that are modified they are placed on submodules.

# Software on which the test was performed:
- Java version: JDK 17.0.6 Oracle Corporation 2023-01-17
- Eclipse IDE for Enterprise Java and Web Developers (includes Incubating components)
Version: 2024-03 (4.31.0)
Build id: 20240307-1437
- Tomcat: 10.1.11
- GWT Eclipse Plugin 4.0.1.202402121339
- GWT 2.11.0

# The test application (attached):
The application consists of 2 modules:
- testGWT (main)
- testShared (submodule)

The messages are present on the testShared submodule in the MyMessages.properties file.

# Steps to reply:
1. Prepare Eclipse 2024-03 with JDK 17, Tomcat 10.1 and GWTPlugin 4.0.1.202402121339
2. Import the 2 modules (testGWT and testShared) into Eclipse
3. Create a GWT Development Mode (CodeServer) configuration and set the appropriate -launcherDir option.
In my environment: -launcherDir X:\Code\projBase\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\testGWT test.gwt.sample.TestGWT
4. Run testGWT under the Tomcat server you configured in Eclipse.
5. Load the application from browser: http://localhost:8080/test/testgwt/TestGWT.html
6. When you see the "GO4" button, click to view the message: "This is my message"
7. Open the MyMessages.properties file and change the message1 message to "This is my message updated"
8. Reload the application from browser: http://localhost:8080/test/testgwt/TestGWT.html
9. Click on the "GO4" button to view the message

# Expected results:
- In step 9 I expect to see the message "This is my message updated" but instead I keep seeing "This is my message".
- In the Eclipse Console at point 8 I expect to see a recompilation message but instead I see:

GET /recompile/testgwt
Job test.gwt.sample.TestGWT_1_1
starting job: test.gwt.sample.TestGWT_1_1
binding: user.agent=safari
skipped compile because no input files have changed
0,022s total -- Compile completed

[testGWT_2.zip](https://github.com/gwt-plugins/gwt-eclipse-plugin/files/15177199/testGWT_2.zip)

使用所列出的 Eclipse、JDK、Tomcat、GWT Plugin 和 GWT 版本，复现 testGWT 和 testShared 的双模块测试。先修改 MyMessages.properties，并检查 /recompile/testgwt 的输出，尤其是跳过编译的消息。当子模块属性文件中的更改触发重新编译，并且更新后的消息在重新加载后出现时，即表示完成。

由索引模型根据 Issue 内容生成。