[Feature Request] Add ability to include custom binaries (not app bundles) into code signing pipeline

## Task/Context
I want to include `ffmpeg` executables (not dylib-s, but "exe") in my app bundle and run them via `Process.Start()`. The resulting app bundle should be able to pass apple notarization and review processes.
A typical solution is to add `ffmpeg` as a `Content` and sign it.
```

PreserveNewest

```

## Current NET SDK Implementation
By default, the .NET build pipeline won't sign `ffmpeg`, as it is just a file without an extension.

## Current Implementation Customization Options
We have the following options to customize the signing process:
* `` msbuild item group, which allows adding an _application bundle_ (but not a ordinal executable) to the "to be signed" list. This works well if my helper application _is_ an app bundle. Unfortunately, it does not work for `ffmpeg`, which is a single console executable.
* `` msbuild item group, which allows using pre-signed binaries (and not to break the signature during the build). This may be helpful for the binaries built by me, but not for the ready-to-use binary builds of the `ffmpeg` taken from the official ffmpeg site.
* Fully custom logic like ``. This works, but making it consistent with the project signing settings requires a lot of code and finally it is a little bit "code smell."

So, none of the existing options provides an easy-to-use and robust solution.

## Proposal
Extend or rework the `` functionality to allow signing not only app bundles but also single executable files.

Note: such a binaries (e.g. `ffmpeg`) are often distributed as a bundles containing multiple executables (e.g. `ffmpeg` and `ffprobe`) as well as their dependencies (`dylib`s, etc). Therefore, the wildcards support (to be able to include the whole folder with all its content and, ideally, somehow filter out non-binary/non-signable files) will be more important in this scenario than in case when including app bundles.