internal: pass db_lt to the inner_fn

[davidbarsky]

This is necessary to support passing interned structs to queries in the query group imitation macro: https://github.com/davidbarsky/db-ext-macro/.

(I'll upstream that macro to Salsa, promise! The code quality is bad, however...)

[netlify]

✅ Deploy Preview for salsa-rs canceled.

Name	Link
🔨 Latest commit	c2ce00d
🔍 Latest deploy log	https://app.netlify.com/sites/salsa-rs/deploys/673f52634bc1cb0008bad837

[codspeed-hq]

CodSpeed Performance Report

Merging #617 will not alter performance

_{Comparing davidbarsky:david/pass-db-lt-to-inner-fn (c2ce00d) with master (32f8ee9)}

Summary

✅ 8 untouched benchmarks

[MichaReiser]

Could you add demonstrating its use case?

[davidbarsky]

Pushed a fix for the unused lifetime lint.

Could you add demonstrating its use case?

@MichaReiser Uh, probably. Without porting my macro over, it might be a little challenging, but I think I can add it as a desugared version.

[davidbarsky]

Closing this, as this isn't needed anymore.