ActivityInput.DefaultSyntax is not properly respected by the designer

Setting the `DefaultSyntax` of an `[ActivityInput]` does properly configure the `elsa-property-editor`/`elsa-multi-expression-editor` component(s) with the default syntax. This causes the UI to always treat the default syntax as if it were `SyntaxNames.Literal` but the server to use the `DefaultSyntax` configured in the `[ActivityInput]`.

This is specifically with a `DefaultSyntax = SyntaxNames.Liquid, UIHint = ActivityInputUIHints.MultiLine`. Removing the `UIHint` appears to make it bind to the correct expression, however, it only presents a single line for input.