Checkpoint for go/af-guice-best-practices doc refresh
The CL was starting to get a bit more than plain cut-and-paste, and I wanted to get it in before continuing.
You'll see, for example, that in one case, I re-homed a best practice inside of another pre-existing best practice.
In a couple of other places I removed Google-only content in favor of more generally-worded content.
PiperOrigin-RevId: 337392075
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