Improves how -Include works

[santisq]

Before this PR, -Include would only target files and not directories. It would also display folders where no file matched the pattern, for example:

PS ..\pwsh> pstree -include *.ps1

   Source: C:\Users\User\Documents\pwsh

Mode            Length Hierarchy
----            ------ ---------
da---        133.46 KB pwsh
-a---        487.00  B ├── test1.ps1
-a---          7.57 KB ├── test2.ps1
d----         12.30 KB ├── testcs
d----         25.17 KB │   ├── obj
d----          0.00  B │   │   └── Debug
d----          0.00  B │   └── bin
d----          0.00  B │       └── Debug
d----        386.00  B ├── consoleapp
d----          5.00 KB │   ├── obj
d----          0.00  B │   │   └── Debug
d----          0.00  B │   └── bin
d----          0.00  B │       └── Debug
d----          1.67 KB └── .vscode

With the new version, -Include now properly can target folders and also exclude sub-trees where no leaf matched the include pattern:

PS ..\pwsh> pstree -include *.ps1

   Source: C:\Users\User\Documents\pwsh

Mode            Length Hierarchy
----            ------ ---------
da---        133.46 KB pwsh
-a---        487.00  B ├── test1.ps1
-a---          7.57 KB └── test2.ps1

[codecov]

Codecov Report

Attention: Patch coverage is 99.58159% with 1 line in your changes missing coverage. Please review.

Project coverage is 97.63%. Comparing base (6c617ee) to head (3567b8b).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
src/PSTree/PSTreeFile.cs	94.73%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
+ Coverage   96.83%   97.63%   +0.79%     
==========================================
  Files          16       16              
  Lines         569      591      +22     
  Branches       60       67       +7     
==========================================
+ Hits          551      577      +26     
+ Misses         17       12       -5     
- Partials        1        2       +1     

Flag	Coverage Δ
PS-5.1	97.63% <99.58%> (+1.32%)	⬆️
PS-7_Linux	97.29% <99.58%> (+1.33%)	⬆️
PS-7_Windows	97.63% <99.58%> (+1.32%)	⬆️

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