Default lints should correspond to rustc

Summary

I would expect that rust-analyzer, with default settings, would report the same lints (warnings, errors, etc.) as rustc

Details

Currently this is not the case; for example I also see messages about these:

• inactive-code — this may have a special purpose in some editors? In Kate it's more annoying than useful, but that may be just Kate.
• remove-unnecessary-else — nearest equivalent is Clippy's redundant_else?

The default enabled lints also do not correspond to Clippy's default lints (there is a note in the manual about enabling Clippy by default).

Motivation

I would (naively) expect that a project which is clean (reports no lints) under cargo check is also clean under rust-analyzer, and vice-versa. This makes it easier for developers using different tools to collaborate on a project.

Further motivation: the rust-analyzer project should probably not be responsible for choosing which lints are enabled by default (especially when both rustc and clippy already do this).

Start by comparing rust-analyzer's default diagnostics with rustc via cargo check, then review the examples in the issue and Clippy's default lint list. Done means the default rust-analyzer lints consistently match the intended rustc behavior, with a clear decision about how Clippy-related lints are handled.