Nav Unification - implement conditionals for static fallback nav data

[getdave]

Sub Issue of #45435

Once #45836 is merged we will have a static copy of a basic admin menu which we can use to render instantly as the user loads Calypso.

However, there are certain conditions that determine which items should/shouldn't be shown to a user. These need to be implemented within the "static" data. Placeholders already exist, but the conditional logic needs to be written.

[getdave]

@obenland Is it worth tackling this at this stage? It's another level of detail and could take a while.

[obenland]

We can probably backload that.

[mreishus]

I haven't done all of the different flags, just a couple, but requesting a look+review before sinking more time into this. #46785