infra: add PL device testing using a stable PL version

[AbeCoull]

Issue #, if available:

Description of changes: Tests the latest Braket code against the latest release of PennyLane. Includes a tox env for better local testing.

Testing done: tox -e pennylane-device-tests

Merge Checklist

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General

• [ ] I have read the CONTRIBUTING doc
• [ ] I used the commit message format described in CONTRIBUTING
• [ ] I have updated any necessary documentation, including READMEs and API docs (if appropriate)

Tests

• [ ] I have added tests that prove my fix is effective or that my feature works (if appropriate)
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[codecov[bot]]

Codecov Report

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

Project coverage is 100.00%. Comparing base (043a332) to head (67cb7c6). Report is 21 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #264   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            7         7           
  Lines         1242      1242           
  Branches       305       305           
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  Hits          1242      1242           

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[AbeCoull]

Build is expected to fail until https://github.com/amazon-braket/amazon-braket-pennylane-plugin-python/issues/253 is resolved

[AbeCoull]

Is there a way to add this as a tox target so we can run the device tests locally?

@speller26, added tox -e pennylane-device-tests