fix: do not override existingSession setup

[samtsai]

Use existingSession.setup instead of overriding with server stored
session because of string serialization.

This applies the fix mentioned by @bahmutov #17805 (comment)

• Closes Cypress session validation failure results in a 'existingSession.setup is not a function' error #17805

User facing changelog

Fixed an issue with cy.session where hard refresh of a test in open mode would fail to recreate the session due to a TypeError: existingSession.setup is not a function.

How has the user experience changed?

Before

After

PR Tasks

• Have tests been added/updated?
• Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?
• Have new configuration options been added to the cypress.schema.json?

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[emilyrohrbough]

@samtsai This issue has been on my radar for getting Sessions ready for GA support (hopefully soon) and am grateful for your contribution!

[samtsai]

@samtsai This issue has been on my radar for getting Sessions ready for GA support (hopefully soon) and am grateful for your contribution!

Glad to help! I love using Cypress every day and am looking forward to this feature.

[samtsai]

I don't have access to re-run those failing tests but from what I can see I don't think it's caused by my test. The failing one is labeled flaky.

[emilyrohrbough]

@samtsai ahh thanks for calling this out! I've been trying to keep an eye on this and got distracted. Just kicked if off again.

[cypress-bot]

Released in 9.6.1.

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