Update dependencies

[rohan-gandhi-cai]

Description

This PR updates C7n to 0.9.43 and c7n_mailer to 0.6.15, removed python 3.7 and added python 3.12, updated some of the tests to work with the latest pytest, and fixed the dependency issues.

Testing Done

Ran dry runs on our team AWS account.
Tox output:

python3.8: OK (6.48=setup[3.06]+cmd[0.01,0.08,0.10,0.15,3.09] seconds)
py39: OK (4.12=setup[1.18]+cmd[0.01,0.07,0.14,0.19,2.53] seconds)
py312: OK (5.31=setup[1.83]+cmd[0.01,0.08,0.10,0.15,3.14] seconds)
docs: OK (7.25=setup[1.76]+cmd[0.01,0.07,0.11,0.15,4.23,0.14,0.79] seconds)
docker: OK (52.56=setup[1.81]+cmd[0.01,0.07,0.11,0.16,50.40] seconds)
congratulations :) (75.76 seconds)

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