Only load translations for an integration once per test session

[bdraco]

needs #117224

Proposed change

During a production run we cache the translations, but for tests we load english on every test (tests only have english). A new pytest fixture called translations_once with session scope allows translations to be shared between runs. It can be disabled for specific tests by using the disable_translations_once fixture. This sped up my local test runs by ~6%.

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[bdraco]

That advantage air test is flakey. Probably going to need to fix that first since this change seems to make it worse as it likely takes more work out of the loop and now its more flakey