Module level attributes are being parsed before plugins are registered

[draivin]

Previously I was using a plugin to register a MultiModifier, and the plugin users would use a #![modifier] attribute in the entry module of their programs, so the plugin could rewrite anything inside the module.

But on the latest nightly, this results in a compilation error:

error: The attribute `modifier` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)

This leads me to believe that module level attributes are now being parsed before the plugins finish registering.

Tagging @jseyfried.

[jseyfried]

Fixed in #36618 (this was caused by #36214, unintentionally).