Warn, not error, on precompile failure

[timholy]

xref #39905. That has some extra goodies in it so this doesn't replace it, but it is an alternative approach for part of it.

[vtjnash]

I think it is just conceptually flawed here to return a bool. We shouldn't need this much code-generation around doing a function call. It is not very flexible and has a tendency to bit-rot.

For #39905, I considered adding a nowarn::Bool=false default option though. Or warnversion::VersionNumber=VERSION (which warns only if VERSION <= warnversion). Thoughts?

[timholy]

If you think the bool is flawed then sure, let's use your design. If you agree that we sometimes really do want to hard-fail if the precompile fails...what about two keywords, warn::Bool=false, err::Bool=false. Or perhaps mode::Symbol=:silent with :warn and :err as two other options.

I don't yet see the reason to supply a version number, so perhaps you could explain the reasoning there.

[kimikage]

xref: timholy/SnoopCompile.jl#243