Prevent "soft" memory leaks by suggesting to shrink

What it does

Vecs, Strings, and other heap-allocated types, don't automatically shrink their capacity when the len() is small enough. This lint acts as a reminder to shrink whenever there's a call to remove

Lint Name

remove_without_shrink

Category

perf, restriction

Advantage

• reminds to free unused memory
• good for beginners and experienced devs alike, who are unaware of the lack of auto-shrink, or have too much cognitive load (respectively)

Drawbacks

• too many false positives, unless it's smarter (i.e. only triggering if multiple elements are removed at once)

Example

vector.remove(0);

Could be written as:

vector.remove(0);
vector.shrink_to_fit();

Start by reviewing existing Clippy lints for Vec and String removal and capacity handling. Define when remove_without_shrink should trigger, including how to avoid the false positives noted for single removals. Done means the lint behavior, applicability, and tests cover the agreed cases.