bpart: Start enforcing min_world for global variable definitions

[Keno]

This is the analog of #57102 for global variables. Unlike for consants, there is no automatic global backdate mechanism. The reasoning for this is that global variables can be declared at any time, unlike constants which can only be decalared once their value is available. As a result code patterns using Core.eval to declare globals are rarer and likely incorrect.

[Keno]

Distributed test failure is JuliaLang/Distributed.jl#125.

[DilumAluthge]

Needs #57169 I presume.

[DilumAluthge]

@Keno Here's the test failure now:

Error in testset rebinding:
Error During Test at /cache/build/tester-amdci5-13/julialang/julia-master/julia-7f6d503f8b/share/julia/test/testdefs.jl:24
  Got exception outside of a @test
  LoadError: invalid redefinition of constant Rebinding.Foo
  Stacktrace:

[IanButterworth]

I assume this test noise from the docs tests was introduced here

      From worker 6:	WARNING: Detected access to binding `NoDocStrings.##meta#60` in a world prior to its definition world.
      From worker 6:	  Julia 1.12 has introduced more strict world age semantics for global bindings.
      From worker 6:	  !!! This code may malfunction under Revise.
      From worker 6:	  !!! This code will error in future versions of Julia.
      From worker 6:	Hint: Add an appropriate `invokelatest` around the access to this binding.
      From worker 6:	WARNING: Detected access to binding `DocRefTests.##meta#60` in a world prior to its definition world.
      From worker 6:	  Julia 1.12 has introduced more strict world age semantics for global bindings.
      From worker 6:	  !!! This code may malfunction under Revise.
      From worker 6:	  !!! This code will error in future versions of Julia.
      From worker 6:	Hint: Add an appropriate `invokelatest` around the access to this binding.