Redesign and improve reporter error display

[chrisbreiding]

• Closes Assertion diff is not shown when an assertion fails and is retried #6722
• Closes Assertions failures on DOM elements show unexpected diffs when they weren't retried #6723

Partial work originally pulled from #3930

• Add markdown support
• Collapse stacktrace
• Separate docs url and add link in reporter
• Refactor error utils

PR Tasks

• Have tests been added/updated?
• Has the original issue been tagged with a release in ZenHub?
• Has a PR for user-facing changes been opened in cypress-documentation?
• N/A Have API changes been updated in the type definitions?
• N/A Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

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User Experience

• The feature/bugfix is self-documenting from within the product.
• The change provides the end user with a way to fix their problem (no dead ends).

Functionality

• The code works and performs its intended function with the correct logic.
• Performance has been factored in (for example, the code cleans up after itself to not cause memory leaks).
• The code guards against edge cases and invalid input and has tests to cover it.

Maintainability

• The code is readable (too many nested 'if's are a bad sign).
• Names used for variables, methods, etc, clearly describe their function.
• The code is easy to understood and there are relevant comments explaining.
• New algorithms are documented in the code with link(s) to external docs (flowcharts, w3c, chrome, firefox).
• There are comments containing link(s) to the addressed issue (in tests and code).

Quality

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• There are no irrelevant comments left in the code.
• Tests are testing the code’s intended functionality in the best way possible.

Internal

• The original issue has been tagged with a release in ZenHub.

[cypress]

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Test summary

3263 • 0 • 49 • 0

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Run details

Project	cypress
Status	Passed
Commit	b6c9631
Started	Mar 13, 2020 6:02 PM
Ended	Mar 13, 2020 6:08 PM
Duration	05:33 💡
OS	Linux Debian - 10.0
Browser	Firefox 72

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