Add minor fix to VList and VTag to conform with #820

[trivigy]

Basically this just fixes the html macro children processing for Vlist and VTag the same way I implemented it in VComp.

[trivigy]

@jstarry the changes in tests/macro/html-block-fail.stderr are purely cosmetic. The same fails still fail but the error messages just changed a little bit.

[jstarry]

@trivigy your changes introduced in #820 created a regression. See #842

Could you please create a new PR that:

1. Re-introduces changes from Improve nested html! expansion by unwrapping VNodes #820
2. Includes the changes here in Add minor fix to VList and VTag to conform with #820 #835
3. Fixes the regression in if and else have incompatible types: VChild VNode #839