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/vagrant/vagrant.go

@@ -130,7 +130,7 @@ func EnumeratePackageVersions(ctx *context.Context) {
 
 	ctx.JSON(http.StatusOK, &packageMetadata{
 		Name:        pds[0].Package.Name,
-		Description: pds[len(pds)-1].Metadata.(*vagrant_module.Metadata).Description,
+		Description: packages_model.DescriptorMetadata[*vagrant_module.Metadata](pds[len(pds)-1]).Description,
 		Versions:    versions,
 	})
 }