GH-106747: Make pathlib ABC globbing more consistent with glob.glob()

[barneygale]

When expanding ** wildcards, ensure we add a trailing slash to the topmost directory path. This matches glob.glob() behaviour:

>>> glob.glob('dirA/**', recursive=True)
['dirA/', 'dirA/dirB', 'dirA/dirB/dirC']

This does not affect pathlib.Path.glob(), because trailing slashes aren't supported in pathlib proper.

• Issue: Glob behavior is inconsistent across libraries #106747

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD14 3.x has failed when building commit 1b1f839.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/1232/builds/1259) and take a look at the build logs.
4. Check if the failure is related to this commit (1b1f839) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/1232/builds/1259

Failed tests:

• test.test_multiprocessing_fork.test_processes

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 8, done.        
remote: Counting objects:  12% (1/8)        
remote: Counting objects:  25% (2/8)        
remote: Counting objects:  37% (3/8)        
remote: Counting objects:  50% (4/8)        
remote: Counting objects:  62% (5/8)        
remote: Counting objects:  75% (6/8)        
remote: Counting objects:  87% (7/8)        
remote: Counting objects: 100% (8/8)        
remote: Counting objects: 100% (8/8), done.        
remote: Compressing objects:  14% (1/7)        
remote: Compressing objects:  28% (2/7)        
remote: Compressing objects:  42% (3/7)        
remote: Compressing objects:  57% (4/7)        
remote: Compressing objects:  71% (5/7)        
remote: Compressing objects:  85% (6/7)        
remote: Compressing objects: 100% (7/7)        
remote: Compressing objects: 100% (7/7), done.        
remote: Total 8 (delta 1), reused 5 (delta 1), pack-reused 0        
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HEAD is now at 1b1f8398d0 GH-106747: Make pathlib ABC globbing more consistent with `glob.glob()` (#115056)
Switched to and reset branch 'main'

configure: WARNING: pkg-config is missing. Some dependencies may not be detected correctly.