chore: Add cancellation support for PdfBuilder operation

[filzrev]

This PR intended to fix issue #9870.

Currently when running docfx pdf command.
Ctrl+C command interruption is not accepted.
So I've added codes to manually cancel running operations.

Note

Playwright don't supports cancellationToken parameters.
So it need manually cancel operation by dispose playwright context.

Specre.Console don't support native cancellation support .
So PdfCommand/DefaultCommand is not modified. (It need to migrate to AsyncCommand in future)
https://github.com/spectreconsole/spectre.console/issues/701

What's changed in this PR

1. Add cancellationToken parameter to PdfBuilder's public APIs
2. Add Console.CancelKeyPress event handlers to cancel running operations
3. Add cancellationToken parameter to following methods
   3.1. WebApplication.Start
   3.2. ParallelOptions parameter of Parallel.Foreach
4. Call cancellationToken.ThrowIfCancellationRequested() inside loop.
5. Rename outputPath parameter to pdfOutputPath.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 13 lines in your changes missing coverage. Please review.

Project coverage is 79.32%. Comparing base (fe673ec) to head (253d001).
Report is 503 commits behind head on main.

Files with missing lines	Patch %	Lines
src/Docfx.App/PdfBuilder.cs	65.38%	8 Missing and 1 partial ⚠️
src/docfx/Models/CancellableCommandBase.cs	70.00%	3 Missing ⚠️
src/docfx/Models/PdfCommand.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10460      +/-   ##
==========================================
+ Coverage   74.31%   79.32%   +5.00%     
==========================================
  Files         536      548      +12     
  Lines       23189    23655     +466     
  Branches     4056     4064       +8     
==========================================
+ Hits        17234    18764    +1530     
+ Misses       4853     3720    -1133     
- Partials     1102     1171      +69     

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[filzrev]

What's changed on latest commit.

1. CancellableCommandBase.cs
Add abstract CancellableCommandBase class to support CancellationToken.
It subscribe following signal events and pass cancellation token to command.

• SIGINT: It happens on Ctrl+C key pressed.
• SIGQUIT: It happens on Ctrl+Break key pressed.
• SIGTERM: It used on docker stop for example (On Windows environment it's not used)

See details: https://github.com/spectreconsole/spectre.console/issues/701

2. PdfBuilder.cs
2.1. Remove Console.CancelKeyPress event subscription. Use SIGINT signal instead.
2.2. Modify code to use cancellationToken that is passed as argument.
2.3. Modify code to use .WaitAsync(cancellationToken) instead of Task.When`.

3. DefaultCommand.cs
4. PdfCommand.cs
Modify code to use CancellableCommandBase.

TODO
Following tasks are not scope of this PR.

• Implement Graceful Shutdown.
• Add CancellationToken support for non-PDF relating commands (Build/Metadata)