User feedback regarding performance

A user left some comments for Java Extension Pack and it's regarding language server performance.

There are two aspects to this problem:

1. The long lag for language server to load bigger projects (~8500 files in this case)
2. Progress update was not effective and the user gets the "stops responding" impression

While @yaohaizh is pushing for 1, @testforstephen could you please help revisit 2?

Here's the source of the comments:
https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack&ssr=false#review-details

未指定文件或测试。首先跟踪 issue 中描述的 language server 加载和进度更新入口点，然后使用一个大约包含 8,500 个文件的项目重现该行为；当启动延迟和无效的进度反馈得到解决并经过验证后，即视为完成。