Add support for v5 Exec protocol when using Kubernetes 1.29+

[jacobtomlinson]

With Kubernetes 1.29 we should be able to use the v5.channel.k8s.io exec protocol to close the stdin channel.

However, things don't seem to be working as expected with the latest kind 1.29 image and I'm getting 403 errors when connecting.

Pushing up a draft to see if the same thing happens in CI.

[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 3 lines in your changes missing coverage. Please review.

Project coverage is 94.64%. Comparing base (673184d) to head (fb11537).
Report is 155 commits behind head on main.

Files with missing lines	Patch %	Lines
kr8s/tests/test_objects.py	71.42%	2 Missing ⚠️
kr8s/_exec.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #270      +/-   ##
==========================================
- Coverage   94.91%   94.64%   -0.27%     
==========================================
  Files          27       27              
  Lines        2871     2878       +7     
==========================================
- Hits         2725     2724       -1     
- Misses        146      154       +8     

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