Add ability to specify a yaml file as parameters

[aidando73]

*Issue #2275

• Adds ability to specify a yaml file as parameters
• Will work for any list yaml files (but not for dictionary yaml files)

Screencast.from.25-08-23.18.45.15.webm

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[aidando73]

Wasn't sure if there was a use case for dictionary yaml documents. Let me know if you guys want to support it.

[codecov-commenter]

Codecov Report

Merging #8133 (f5b7fcd) into v2 (27f75db) will decrease coverage by 0.01%.
Report is 18 commits behind head on v2.
The diff coverage is 82.35%.

@@            Coverage Diff             @@
##               v2    #8133      +/-   ##
==========================================
- Coverage   93.12%   93.11%   -0.01%     
==========================================
  Files         363      363              
  Lines       38291    38308      +17     
  Branches     6127     6130       +3     
==========================================
+ Hits        35657    35670      +13     
- Misses       1963     1968       +5     
+ Partials      671      670       -1     

Files Changed	Coverage Δ
awscli/argprocess.py	91.69% <82.35%> (-0.24%)	⬇️

... and 2 files with indirect coverage changes

[aidando73]

I just realized there's another PR that aims to achieves something similar #5482 but with a different approach.

Up to you guys which approach you want to choose.

[aidando73]

One drawback of my approach is that it's difficult to provide useful error messages; It's difficult to determine whether the argument passed in is an invalid yaml document or shorthand or JSON - since we try and parse the full yaml document.

Alternatives might be:

• Parse yaml files based on file extensions .yml or .yaml (though there might be use cases where file extensions are not .yml or .yaml)
• Go with the yaml:// prefix idea

These would allow better error messages

[aidando73]

The more I think about it, the more file extension based matching makes more sense. Let me know if you want me to redo this PR