REPL: Don't look for missing packages in code that isn't going to be run

[IanButterworth]

Fix #41879

@timholy seem reasonable?

julia> ex = :(using ImageCore)
:(using ImageCore)

julia> if true using ImageCore end
 │ Package ImageCore not found, but a package named ImageCore is available from a registry. 
 │ Install package?
 │   (@v1.8) pkg> add ImageCore 
 └ (y/n/o) [y]: n

[vtjnash]

Is it unreasonable/bad though to think this might be passed to eval?

[timholy]

As suggested by @vtjnash, perhaps eval(:(using ImageCore)) might be a missing case. Overall, though, I'd say it's OK if it misses some suggestions. I think over-suggesting is the more serious flaw.

[StefanKarpinski]

This seems like a good compromise to me. Using eval to load packages seems advanced/rare enough that not having the auto install behavior is ok.