gh-133213: Add tests for string.templatelib.TemplateIter

[sobolevn]

I did not include pickle tests, because I found a problem with it. I will open a separate issue for that, it will require some C code modifications.

• Issue: PEP 750: Improve TemplateIter tests #133213

[AA-Turner]

Also test two interpolations next to each other?

[sobolevn]

We already have tests for the iteration, I just test that direct iter() call work correctly.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot aarch64 Fedora Stable LTO 3.x (tier-2) has failed when building commit 0e21ed7.

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/#/builders/336/builds/6843) and take a look at the build logs.
4. Check if the failure is related to this commit (0e21ed7) 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/#/builders/336/builds/6843

Failed tests:

• test_functools

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

==

Click to see traceback logs

remote: Enumerating objects: 11, done.        
remote: Counting objects:   9% (1/11)        
remote: Counting objects:  18% (2/11)        
remote: Counting objects:  27% (3/11)        
remote: Counting objects:  36% (4/11)        
remote: Counting objects:  45% (5/11)        
remote: Counting objects:  54% (6/11)        
remote: Counting objects:  63% (7/11)        
remote: Counting objects:  72% (8/11)        
remote: Counting objects:  81% (9/11)        
remote: Counting objects:  90% (10/11)        
remote: Counting objects: 100% (11/11)        
remote: Counting objects: 100% (11/11), done.        
remote: Compressing objects:  20% (1/5)        
remote: Compressing objects:  40% (2/5)        
remote: Compressing objects:  60% (3/5)        
remote: Compressing objects:  80% (4/5)        
remote: Compressing objects: 100% (5/5)        
remote: Compressing objects: 100% (5/5), done.        
remote: Total 6 (delta 5), reused 1 (delta 1), pack-reused 0 (from 0)        
From https://github.com/python/cpython
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HEAD is now at 0e21ed7c09c gh-133213: Add tests for `string.templatelib.TemplateIter` (#133215)
Switched to and reset branch 'main'

make: *** [Makefile:2453: buildbottest] Error 2