Optimization work.

[galenhuntington]

This PR addresses old annotations and settings to squeeze out performance, which are barely relevant today, and may indeed be obsolete:

• Two fields in HState were inadvertently not strict; this is fixed.
• A few other data fields are made strict which seem that they clearly should be.
• -funbox-strict-fields is dropped per a conversation with Claude. Modern GHC has better heuristics than it used to, and this setting appears to make performance microscopically worse.
• Nearly all INLINEs are dropped. Claude advised me to keep them, but I think that is out of bias towards the status quo ante, whereas I see unnecessary annotations as distracting clutter. Apparently they do nothing since inlining happens anyway since GHC knows they're small, and most are in-module so there's not even a need. I kept the one that is cross-module, though it is small enough to likely not need it.
• Nearly all UNPACKs are dropped. Claude similarly advised me to keep them, but I see no benefit. The Msg fields in question are immediately copied into a Just where they're boxed anyway. The style in Segment is looked up in a map and so presumably is always boxed at that point (plus it's almost always pulled from a data structure where it's already boxed, so why flatten?). I only kept the Segment ByteString as unpacked since maybe in some cases there is no boxing.

In general, for this app, these are imperceptible sub-microsecond differences, so my inclination is to not annotate, that is, not second-guess GHC's defaults with extra stuff when it doesn't matter anyway. But if it's "right" to do it, it still makes sense, and there is a case for leaving a couple undisturbed. Hence the above choices.

Unrelatedly, I tweaked a test from the last PR to spare an import, and trimmed a few comment lines.