chore: update dependencies and dev branch

[zetlen]

Description

Replacement for #962.
Update version strings and package dependencies in preparation for 2.1.0 release.

• Set all package version strings to 2.1.0-dev, since we would cut any proposed hotfix from the most recent release tag, and therefore anything we release from develop would be at least a minor version
• Update minor and patch versions of many dependencies
• Update
• Set dependencies back to caret ranges instead of release-oriented stricter tilde ranges
• Adjust jest config for new API
• Adjust babel config for new Jest mock search behavior

Related Issue

N/A, maintenance chore

Motivation and Context

Keep dependencies up to date with latest bug and stability fixes.

Verification

If CI passes and metrics don't worsen, this should be good.

How Has This Been Tested?

Ran all relevant build, watch, and test scripts.

All package deps changed, no production code changes.

Checklist:

• I have read the CONTRIBUTING document.
• I have linked an issue to this PR.
• I have indicated the change type and relevant package(s).
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All CI checks are green (linting, build/deploy, etc).
• At least one core contributor has approved this PR.

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[coveralls]

Coverage increased (+4.4%) to 76.78% when pulling 5d8897d on zetlen/upgrade-deps-for-dev-post-2.0.0 into a2b7a94 on develop.