feat: table: expandable config improvements

[dkilgore-eightfold]

SUMMARY:

• Updates default Expand Icon Button to match latest UX specifications
• Updates Tree indentation to include the button in the indent
• Fixes expandIcon prop so that custom expand cell content may be used along with a custom expand icon button
• Adds new story demonstrating custom expandIcon
• Separates CheckBox and Radio Selection stories to better communicate the options
• Ensures the Selection component is horizontally centered in its cell
• Updates UTs

Before: https://github.com/EightfoldAI/octuple/assets/99700808/ba7594e2-8ce4-49e7-80ea-582782a051c6

After: https://github.com/EightfoldAI/octuple/assets/99700808/df14636c-a21c-4328-85e9-c7b5e5d4c0a1

JIRA TASK (Eightfold Employees Only):

ENG-76971

CHANGE TYPE:

• [ ] Bugfix Pull Request
• [x] Feature Pull Request

TEST COVERAGE:

• [ ] Tests for this change already exist
• [x] I have added unittests for this change

TEST PLAN:

Pull the PR branch and run yarn and yarn storybook. Verify the Table stories behave as expected.

[codesandbox-ci[bot]]

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Sandbox	Source
React	Configuration

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (ebea12c) 84.81% compared to head (3fd3196) 84.82%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #777 +/- ## ========================================== + Coverage 84.81% 84.82% +0.01% ========================================== Files 999 999 Lines 19528 19531 +3 Branches 7281 7284 +3 ========================================== + Hits 16563 16568 +5 + Misses 2885 2883 -2 Partials 80 80 ```

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