Namedtuple bugfix

[rlizzo]

Motivation and Context

Why is this change required? What problem does it solve?:

Fix incompatibility between set of possible names an Arrayset can take vs those valid namedtuple field names.

If it fixes an open issue, please link to the issue here:

• closes [BUG REPORT] NamedTuple doesn't like all the name formats hangar allows #158

Description

Describe your changes in detail:

• Use built in namedtuple method to rename invalid fields with a positional index.
• Fully documented behavior and implications; highlighting remaining limitations which remain even with this fix.
• full test coverage?

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Documentation update
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Is this PR ready for review, or a work in progress?

• Ready for review
• Work in progress

How Has This Been Tested?

Put an x in the boxes that apply:

• Current tests cover modifications made
• New tests have been added to the test suite
• Modifications were made to existing tests to support these changes
• Tests may be needed, but they are not included when the PR was proposed
• I don't know. Help!

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have signed (or will sign when prompted) the tensorwork CLA.
• I have added tests to cover my changes.
• All new and existing tests passed.

[rlizzo]

@hhsecond take a look and let me know if this is a proper solve for the issue?

[codecov]

Codecov Report

Merging #161 into master will increase coverage by <.01%.
The diff coverage is 96.98%.

@@            Coverage Diff             @@
##           master     #161      +/-   ##
==========================================
+ Coverage   95.21%   95.22%   +<.01%     
==========================================
  Files          63       63              
  Lines       11196    11393     +197     
  Branches      964      974      +10     
==========================================
+ Hits        10660    10848     +188     
- Misses        357      363       +6     
- Partials      179      182       +3

Impacted Files	Coverage Δ
src/hangar/checkout.py	92.43% <100%> (+0.19%)	⬆️
tests/test_checkout_arrayset_access.py	99.13% <96.77%> (-0.71%)	⬇️
tests/test_remotes.py	97.97% <0%> (-0.55%)	⬇️

[hhsecond]

Looks good