fix(serverless): Check if cloud event callback is a function (#9044)

[tcoyze]

Closes #9044

Adds relevant tests for testing handlers that return promises.

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[AbhiPrasad]

Thank you for a PR! Could you add a test to https://github.com/getsentry/sentry-javascript/blob/f2d903b1e034bd2c388fb0d8d63ce7fce8ef9ef9/packages/google-cloud-serverless/test/gcpfunction/cloud_event.test.ts about this?

[tcoyze]

Thank you for a PR! Could you add a test to https://github.com/getsentry/sentry-javascript/blob/f2d903b1e034bd2c388fb0d8d63ce7fce8ef9ef9/packages/google-cloud-serverless/test/gcpfunction/cloud_event.test.ts about this?

@AbhiPrasad Tests added! Thanks for the review 🙌

[AbhiPrasad]

Thank you for you contribution!

[AbhiPrasad]

ah seems like theres some formatting issues. https://github.com/getsentry/sentry-javascript/actions/runs/8787015686/job/24111825459?pr=11701

Running yarn fix in the package root should handle that!

[tcoyze]

FWIW I have been having build issues, apologies for the failed checks. Resolving those now!

[tcoyze]

@AbhiPrasad Thanks! Fixed that, and rebased 😄

[AbhiPrasad]

develop reflects our current work on 8.0.0, the next major version. I'll take care of backporting this change to the 7.0.0 set of SDKs - #11729

Thanks!