pkgload 1.2.0

• Fix test failure in R 4.1 with regards to S4 method registration

• load_all() now preserves existing namespaces in working order. In
  particular, it doesn't unload the package's shared library and keeps
  it loaded instead. When reloading, a copy of the SO for the new
  namespace is loaded from a temporary location. These temporary SOs
  are only unloaded on GC and deleted from their temporary location
  via a weak reference attached to the namespace.

  This mechanism ensures that lingering references to the namespace
  keep working as expected. Consequently the namespace
  propagation routine that was added to pkgload as a workaround has
  been removed.

  Note that .Call() invocations that pass a string symbol rather
  than a structured symbol may keep crashing, because R will look into
  the most recently loaded SO of a given name. Since symbol
  registration is now the norm, we don't expect this to cause much
  trouble.

• load_all() no longer forces all bindings of a namespace to avoid
  lazy-load errors. Instead, it removes exported S3 methods from the
  relevant tables.

  • This improves the loading behaviour with packages that define
    objects in their namespaces lazily (e.g. with delayedAssign()).

  • This also makes load_all() more predictable after a method has
    been removed from the package. It is now actually removed from the
    generic table. It would previously linger until R was restarted.

• If load_all() attaches testthat, it automatically suppresses conflicts.