add lint infallible_try_from

[ComputerDruid]

Looks for TryFrom implementations with uninhabited error types and suggests to implement From instead.

Fixes #2144

---

changelog: Added [infallible_try_from] to nursery

[rustbot]

r? @blyxyas

rustbot has assigned @blyxyas.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[ComputerDruid]

r? @llogiq

Written at the workshop during RustWeek

[llogiq]

This is a good start. The code is still failing dogfood, where clippy lints itself. Looking at the suggestions, you should change the "default lint description" in the lint definition block, and use a sym instead of comparing idents with strs in line 55. Apart from that, I have only a very small nit. Once that's dealt with, I'll start the Final Comment Period for adding this lint.

[ComputerDruid]

Should be ready to go now