Add elapsed_instant lint

[guerinoni]

Closes #8603

• Followed [lint naming conventions][lint_naming]
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

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changelog: [elapsed_instant]: Add lint

[rust-highfive]

r? @Alexendoo

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[Alexendoo]

Hello! Thanks for the PR

[Alexendoo]

Thanks again just some documentation/formatting left and it'll be good to go

[guerinoni]

@Alexendoo Thank you so much :)

[Alexendoo]

Thanks!

@bors r+

For what it's worth you don't need to hit the request review button. Since we get a notification on each commit after we're assigned I don't think it actually does anything

[bors]

📌 Commit 0696624 has been approved by Alexendoo

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0696624 with merge 00e59cd...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Alexendoo
Pushing 00e59cd to master...