chore: enable forcetypeassert linter, fix issues (#38804)

Enable [`forcetypeassert`](https://github.com/gostaticanalysis/forcetypeassert)
linter to prevent unchecked type assertions. ~650 issues fixed, most
fixes were clean, some use `setting.PanicInDevOrTesting`.

The only behaviour changes are where code would previously send a 500 error
or panic, a 4xx error is now emitted.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/api/packages/cargo/cargo.go

@@ -127,7 +127,7 @@ func SearchPackages(ctx *context.Context) {
 		crates = append(crates, &SearchResultCrate{
 			Name:          pd.Package.Name,
 			LatestVersion: pd.Version.Version,
-			Description:   pd.Metadata.(*cargo_module.Metadata).Description,
+			Description:   packages_model.DescriptorMetadata[*cargo_module.Metadata](pd).Description,
 		})
 	}