feat: Add before:spec event

[chrisbreiding]

• Addresses TR-543
• Partially addresses Add new plugin events 'before:spec', 'after:spec', 'before:run', 'after:run' #6665

User facing changelog

• You can now listen to a before:spec event in the plugins file. See the documentation for more information (TODO: link to doc).

Additional details

• The event fires before a spec is run.

• It only fires in run mode.

• The event handler receives one argument, an object with different versions of the spec file/path.

   {
     name: 'login_spec.js',
     relative: 'cypress/integration/login_spec.js',
     absolute: '/Users/janelane/app/cypress/integration/login_spec.js',
   }

PR Tasks

• Have tests been added/updated?
• Has the original issue or this PR been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation? Add doc for before:spec event cypress-documentation#3393
• Have API changes been updated in the type definitions?
• Have new configuration options been added to the cypress.schema.json?

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[cypress]

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Test summary

9156 • 0 • 118 • 3 • 1

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Run details

Project	cypress
Status	Passed
Commit	876e8f2
Started	Dec 16, 2020 8:55 PM
Ended	Dec 16, 2020 9:08 PM
Duration	12:56 💡
OS	Linux Debian - 10.5
Browser	Multiple

View run in Cypress Dashboard ➡️

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Flakiness

	cypress/integration/retries.ui.spec.js		1
1	runner/cypress retries.ui.spec > opens attempt on each attempt failure for the screenshot, and closes after test passes

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This comment has been generated by cypress-bot as a result of this project's GitHub integration settings. You can manage this integration in this project's settings in the Cypress Dashboard

[jennifer-shehane]

@chrisbreiding I'd like some clarification on how this event runs when run via cypress open and selecting 'Run all interactive specs' because this will trip some people up I think.

[flotwig]

looks good

[cypress-bot]

Released in 6.2.0.

This comment thread has been locked. If you are still experiencing this issue after upgrading to
Cypress v6.2.0, please open a new issue.