New lint: vec_init_then_push

[Jarcho]

fixes: #1483

This will trigger on new, default, and with_capacity when the given capacity is less than or equal to the number of push calls. Is there anything else this should trigger on?

changelog: Added lint: vec_init_then_push

[rust-highfive]

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[llogiq]

I like this addition! Just a small nit: I'd make use of inference to keep the docs lean.

Also I think the Changelog line in the PR description should be the last line.

[llogiq]

Thank you! @bors r+

[bors]

📌 Commit 7b5f549 has been approved by llogiq

[bors]

⌛ Testing commit 7b5f549 with merge 976850b...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 976850b to master...