chore: Add custom file copy logics for template files

[filzrev]

This PR intended to resolve #9183 issue.

When running docfx build command with multiple times.
There are unnecessaries operations that overwrite identical files.

This PR add features to skip this operations when template files is not changed.
It's required when using something like dotnet watch scenarios.

What's included in this PR

• Add custom template file copy logics for FileStream.
  • Skip file copy operation when following conditions met.
    1. Output file is already exists.
    2. Files length are same.
    3. Files LastWriteTime is same.
  • If above condition is not met. Use File::Copy API to preserve original LastWriteTime.
• Add PreallocationSize settings for FileStream

Benchmark Results
I've tested on samples/seed project and measuring TemplateProcessor::CopyTemplateResources elapsed times.

1. When it can skip file copy. it's running 10x faster, (e.g. 86.7 [ms] -> 8.0 [ms])
2. When it needs to copy new file and overwrite files.
   It's running slightly slower about 10% (e.g. 86.7 [ms] -> 96.4 [ms])
   I thought it's because of following reasons
   • File.Copy API requires additional operations (e.g. file's attribute copy)
   • It need to open file twice (Open FileStream. then call File::Copy)

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
...ocfx.Build/TemplateProcessors/TemplateProcessor.cs	64.13% <46.15%> (-14.45%)	⬇️

📢 Thoughts on this report? Let us know!.

[KalleOlaviNiemitalo]

Starting from .NET 7.0, File.Copy can make a copy-on-write clone on some file systems, consuming less time and disk space than a full copy of the file content. That is thus a good change even if the copy cannot be skipped entirely.

[yufeih]

Look good. Thank you @filzrev !