feat: add visitor SidecarVisitor and Sidecar action struct

[sebastiantia]

What changes are proposed in this pull request?

This PR introduces the Sidecar action and its associated SidecarVisitor.

This action and visitor is used for the V2 checkpoints Reader/Writer table feature.

resolves #668

Note: PR also simplifies some conditional flags detailed in issue: #672

How was this change tested?

• Ensure schema projection to Sidecar works
• Ensure that the visitor correctly extracts Sidecar actions

[sebastiantia]

This comment is quoted from the protocol linked here.

I am assuming this means we will need to handle both cases where the path is:

1. just the file name of the sidecar files
2. the absolute path (including parent directories)

Or can we assume that implementations are not only encouraged, but DO simply store the file name of the sidecar files as the path?

Delta spark assumes that path is just the file name:
https://github.com/delta-io/delta/blob/990c8e8aedb69a1660e7780ab1d1a19f5c95615f/kernel/kernel-api/src/main/java/io/delta/kernel/internal/replay/ActionsIterator.java#L274

Can I get a 👍 to do the same?

[codecov]

Codecov Report

Attention: Patch coverage is 84.72222% with 11 lines in your changes missing coverage. Please review.

Project coverage is 84.14%. Comparing base (06d8dbb) to head (5e31858).

Files with missing lines	Patch %	Lines
kernel/src/actions/visitors.rs	79.62%	4 Missing and 7 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #673      +/-   ##
==========================================
- Coverage   84.14%   84.14%   -0.01%     
==========================================
  Files          77       77              
  Lines       17710    17777      +67     
  Branches    17710    17777      +67     
==========================================
+ Hits        14902    14958      +56     
- Misses       2096     2100       +4     
- Partials      712      719       +7     

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