VSCode - Generate and maintain verible.filelist

[sconwayaus]

The language server expects verible.filelist to list all verilog files to index symbols and the file needs to be generated by the user manually. It would be better if vscode extension generated the verible.filelist and ideally and maintains the file list.

Proposal
Update the vscode extension as follows:

1. Add a command to generate verible.filelist. Settings should allow users to set an include and exclude glob patterns. Write the file to the root of the project directory.
2. On extensions start, check the existence of verible.filelist, and generate if not found. Settings should allow the users to enable/disable automatic generation of verible.filelist.
3. Hook the generate verible.filelist command to file events in the workspace. There seem to be event handlers for onDidCreateFiles, onDidDeleteFiles, onDidRenameFiles.