Add salsa::Update trait bounds to generics when deriving salsa::Update

[MichaReiser]

Support deriving salsa::Update for generic types.

We have a few generic types in ty that are used within interned values, for which deriving salsa::Update currently doesn't work because the derived salsa::Update doesn't work for all Ts, only Ts that implement salsa::Update.

This PR adds a generic constraint to the salsa::Update implementation to every generic type.

[netlify]

✅ Deploy Preview for salsa-rs canceled.

Name	Link
🔨 Latest commit	01c92b9
🔍 Latest deploy log	https://app.netlify.com/projects/salsa-rs/deploys/694512c948469a00084ae052

[codspeed-hq]

CodSpeed Performance Report

Merging #1041 will degrade performances by 4.01%

_{Comparing MichaReiser:update-trait-bounds (01c92b9) with master (e72b228)}

Summary

❌ 1 regression
✅ 12 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	amortized[Input]	2.1 µs	2.2 µs	-4.01%

[MichaReiser]

We need this to update ty. Happy to address any follow up comments

[ibraheemdev]

Looks fine to me, sorry for the late review.