Added optional explicit config parameter to InClusterConfigLoader

[GlassOfWhiskey]

This PR adds an optional client_configuration parameter to the InClusterConfigLoader, aligning its behavior with the one of KubeConfigLoader and allowing users to manage explicit Configuration objects also with this loading path.

Fixes #194

[codecov]

Codecov Report

Merging #196 (e93a845) into master (aa44bfa) will increase coverage by 0.01%.
The diff coverage is 72.22%.

@@            Coverage Diff             @@
##           master     #196      +/-   ##
==========================================
+ Coverage   27.42%   27.43%   +0.01%     
==========================================
  Files         702      702              
  Lines       93764    93776      +12     
==========================================
+ Hits        25712    25725      +13     
+ Misses      68052    68051       -1     

Impacted Files	Coverage Δ
kubernetes_asyncio/config/incluster_config.py	87.75% <37.50%> (+2.64%)	⬆️
kubernetes_asyncio/config/incluster_config_test.py	97.61% <100.00%> (+0.32%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update aa44bfa...e93a845. Read the comment docs.

[tomplus]

@GlassOfWhiskey Good job, thanks for your contribution!

[tomplus]

Released in v22.6.3.