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/web/repo/issue_lock.go

@@ -13,7 +13,7 @@ import (
 // LockIssue locks an issue. This would limit commenting abilities to
 // users with write access to the repo.
 func LockIssue(ctx *context.Context) {
-	form := web.GetForm(ctx).(*forms.IssueLockForm)
+	form := web.GetForm[*forms.IssueLockForm](ctx)
 	issue := GetActionIssue(ctx)
 	if ctx.Written() {
 		return