Fully qualify at-everywhere, fixes #28966. (#32144)

(cherry picked from commit e6734fa)

stdlib/Distributed/src/macros.jl

@@ -172,7 +172,7 @@ Equivalent to calling `remotecall_eval(Main, procs, expr)`.
 """
 macro everywhere(ex)
     procs = GlobalRef(@__MODULE__, :procs)
-    return esc(:(@everywhere $procs() $ex))
+    return esc(:($(Distributed).@everywhere $procs() $ex))
 end
 
 macro everywhere(procs, ex)

stdlib/Distributed/test/distributed_exec.jl

@@ -1535,6 +1535,18 @@ for T in (UInt8, Int8, UInt16, Int16, UInt32, Int32, UInt64)
     @test n == 55
 end
 
+# issue #28966
+let code = """
+    import Distributed
+    Distributed.addprocs(1)
+    Distributed.@everywhere f() = myid()
+    for w in Distributed.workers()
+        @assert Distributed.remotecall_fetch(f, w) == w
+    end
+    """
+    @test success(`$(Base.julia_cmd()) --startup-file=no -e $code`)
+end
+
 # Run topology tests last after removing all workers, since a given
 # cluster at any time only supports a single topology.
 rmprocs(workers())