Provide (default) configurations for sources not listed in CMakeLists.txt, based on file type

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### Brief Issue Summary

Currently, if the C/C++ extension doesn't receive a custom configuration from CMake Tools for a file, it will opportunistically fall back to using the `compilerPath` and `compilerArgs` provided with the custom browse configuration (a `WorkspaceBrowseConfiguration`). Unfortunately, the `WorkspaceBrowseConfiguration` might apply only to C++ files and not C files, or vice versa, as it contains only a single `compilerPath` and `compilerArgs`.

Perhaps CMake Tools could provide appropriate default configurations for files not included in any CMakeLists.txt? If CMake Tools has sufficient information to provide the default `compilerPath` and `compilerArgs` (as it's already is for the `WorkspaceBrowseConfiguration`), but based on a type of file, it could provide that as a configuration for that type of file.

That might let us to remove the current fallback logic, which is currently hindered by the existence of only a single `compilerPath` and `compilerArgs`. More information on that can be found here:

https://github.com/microsoft/vscode-cpptools-api/issues/42
https://github.com/microsoft/vscode-cpptools/issues/9266

### CMake Tools Diagnostics

_No response_

### Debug Log

_No response_

### Additional Information

_No response_

Start by tracing how CMakeLists.txt sources and WorkspaceBrowseConfiguration data are represented in CMake Tools, including the compilerPath and compilerArgs passed to the C/C++ extension. Review the related vscode-cpptools issues for API constraints. Done means files absent from CMakeLists.txt receive appropriate defaults based on file type, without relying on the single shared fallback configuration.

Written by the indexing model from the issue text.