proj package: add versions 5.2.0 and 5.1.0 (#11079)

* Add versions 5.2.0 and 5.1.0
* Avoid adding version 6.0.0: this version has a new API that is
  not compatible with older versions (and dependents may break with
  it)
* Added comment block explaining the problems with version 6.x
* Replace old datumgrid resource (1.7) with new (1.8)
* Add speculative sqlite dependency for when a 6.x version is added