Issue notifications after loading package

[timholy]

Other packages can set up callbacks to be notified about @require blocks. Previously, the notification was issued before Requires set the const for the module name in the package that set up the @require block. This PR changes it so that those notifications are sent afterwards, thus ensuring that the const will be defined by the time "consumers" get notified.

This is a potentially-breaking change. Since it would cause huge [compat] churn to bump the major version, given the considerations below I think we can safely use a minor-version bump:

• Requires' README does not promise any particular ordering.

• This ordering seems to make a bit more sense.

• Revise appears to be the only user of this functionality based on the lack of any other entries in notified_pkgs and a search of JuliaHub

• This change fixes https://github.com/timholy/Revise.jl/issues/658. The bug was triggered by Revise changes that processed inputs eagerly, in response to new locks to make Base.require threadsafe in the upcoming Julia 1.8 release.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@7ff79f6). Click here to learn what that means. The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #106   +/-   ##
=========================================
  Coverage          ?   62.66%           
=========================================
  Files             ?        3           
  Lines             ?       75           
  Branches          ?        0           
=========================================
  Hits              ?       47           
  Misses            ?       28           
  Partials          ?        0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 7ff79f6...4c301db. Read the comment docs.

[timholy]

Given that I see a thumbs-up for @KristofferC, and I doubt anyone else will review this, let's do it and release a new version.