Provide more granularity of progress during Maven import

[fbricon]

When Maven projects are imported, the progress monitor seems stuck at 57% for a long time until all dependencies are resolved. Users might think something is broken (it's really not), see eclipse-che/che#14004. We should try to provide more details on the progress, so as it doesn't appear stuck.

[amisevsk]

+1 for this. When running on Che, resolving dependencies seems to be the most common time for the language server to get OOMKilled (when it doesn't have enough memory allocated), so showing more progress info would help in catching configuration issues on our end.

[synuwxy]

+1 for this. the progress monitor seems stuck at 57% for a long time when running on vscode-java.
Sometimes you must restart vscode let it work