[sdk-platform-java] The order of entries in generated `gapic_metadata.json` and `package-info.java` should be deterministic

Currently, the order entries in `gapic_metadata.json` and `package-info.java` is the same as the corresponding proto files in `BUILD.bazel`.

However, the proto files can be reordered manually which leads to undeterministic output in `gapic_metadata.json` and `package-info.java`.

The entries should be in a deterministic order (e.g., alphabetic order), regardless the order of protos.

首先跟踪 BUILD.bazel 中的 proto 条目如何用于生成 gapic_metadata.json 和 package-info.java。验证重新排列 proto 文件时当前输出是否会发生变化，然后确认无论 BUILD.bazel 中的顺序如何，这两个生成文件都保持相同的确定性顺序。

由索引模型根据 Issue 内容生成。