Unify integ fixture loading and test skipping

[zastrowm]

Description

Two changes to unify the browser & node tests to have a more unified test suite:

1. Update the integ tests to have a single loadFixture method that is usable from the browser & node tests
2. Update shouldRunTests -> shouldSkipBedrockTests to match the naming of shouldSkipOpenAITests; so that we have the same style of "skipping" between the two

Follow-up PRs will:

• Centralize the client creation for Bedrock & OpenAI, giving us a shared way of creating clients
• Share more tests between the browser and node

Notes

• This is a variant of Unify integ tests to run in browser & node #318 and refactor: unify test fixture loading with async API #283

Related Issues

Related to #225 - as part of #283, I realized we couldn't just have a vite import that really works for both

Documentation PR

Type of Change

Refactor

Testing

How have you tested the change?

• I ran npm run check

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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