[WIP] Implement matrix_exp Batching Rule

[samhu1]

Fixes #115992

What does this PR do?

This pull request attempts to add the feature of batching rule to the matrix_exp function since matrix exponentials are extremely expensive to compute, yet very important in many computing and ML problems . It would be great if such computational expensive functions can support batch implementations.

Checklist

• add test cases to test the correct implementation
• add test cases to see interaction with other functions
• request a code review
• add changelogs

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/125086

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As of commit cb7630e with merge base c4b6ed4 ():
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