Modules should record if instruction count instrumentation is present

[iximeow]

Back when we merged support for instruction counts we didn't have an extensible way to record what optional features were enabled, and so the only way to know if the runtime can rely on instruction counting is seeing if the count is zero or not.

These days, we have exactly such a mechanism with ModuleFeatures, so we should pass the existence (or lack of) a --count-instructions flag from lucetc to this struct for later reference.