Passing templates into markup control messes up the @js directive

[tomasherceg]

Yesterday, @exyi found an edge case where this won't work:

<cc:CustomControl>
  <MyTemplate>

    <!-- this should reference the @js directive of the page, not the markup control -->
    <dot:Button Click="{staticCommand: _js.Invoke(...)}" />

    <!-- this should export the named command in the module of the page, not the markup control -->
    <dot:NamedCommand Name="something" Command="{...}" />

  </MyTemplate>
</cc:CustomControl>

We are not sure how to fix this right now, and we decided to solve it after DotVVM 3.0.
A similar issue probably occurs in nested markup controls and with-control-properties binding - we should find a way how to do it reliably and implement it for both situations.

Originally posted by @tomasherceg in #935 (comment)