Show a warning when an excessive number of C/C++ files are discovered in a workspace #10828
Description
The C/C++ extension may take a very long time to tag parse very large projects. Folders containing recursive symlinks can result in a huge number of (the same) files being discovered. Include graph generation can be very slow (and block some operations), as well as other scalability issues (some that block operations).
We've assumed users are opening individual C++ project folders as workspace folders, and perhaps using multi-root workspaces to open multiple individual project folders. Although perhaps not the majority of users, some users may be opening the roots of very large codebases (Linux kernel, large game projects, the Windows OS repo.) Though this can be a convenient way to navigate a large codebase with a single VS Code window, it may lead to unacceptable performance from the C/C++ extension. It may also not be apparent why IntelliSense doesn't work reliably across all C/C++ files, or why a giant tag parser database gets generated.
Perhaps a warning could be displayed when an excessive number of C/C++ files are detected in a workspace.