Revert "Roll engine to 4466d61a993fdbde2cb092b4da9bbef33d1962fe (#192… (#19233)

…30)"

Causes microbenchmarks to start failing. This included the following
engine PR, which appears to be the culprit:
* Remove vmservice_io.main from entry points. (flutter/engine#5625)

This reverts commit 3643790437f36a11e4ed19f76a1865ff3b0f3a4d.