Add comprehensive lazy import tests ported from internal test suite

Port missing test coverage from the internal lazy imports test suite to
cpython's test_lazy_import, covering behaviors not previously tested:

- Dict operations with lazy values (copy, |, update, values/items)
- from X import * resolution behavior with lazy imports
- Submodule laziness (unused submodules stay lazy, side effects)
- Attribute side effects (submodule imports don't overwrite parent attrs)
- Module/variable name collisions (submodule vs variable ordering)
- Deleted module reimport (sys.modules deletion and reimport)
- Circular import resolution (lazy imports breaking circular deadlocks)
- Custom __import__ via exec with lazy imports
- Dict mutation during module loading
- Runtime enable/disable of lazy imports via sys.set_lazy_imports()

Adds supporting test data modules: metasyntactic package hierarchy,
versioned package, module_same_name_var_order packages, circular_import_pkg,
and cycle_with_load_global_pkg.

Author: brittanyrey

Lib/test/test_lazy_import/__init__.py

@@ -0,0 +1 @@
+

Lib/test/test_lazy_import/data/circular_import_pkg/__init__.py

@@ -0,0 +1,2 @@
+from .x import X2
+X2()

Lib/test/test_lazy_import/data/circular_import_pkg/main.py

@@ -0,0 +1,7 @@
+def X1():
+    return "X"
+
+from .y import Y1
+
+def X2():
+    return Y1()

Lib/test/test_lazy_import/data/circular_import_pkg/x.py

@@ -0,0 +1,7 @@
+def Y1():
+    return "Y"
+
+from .x import X2
+
+def Y2():
+    return X2()

Lib/test/test_lazy_import/data/circular_import_pkg/y.py

@@ -0,0 +1 @@
+

Lib/test/test_lazy_import/data/cycle_with_load_global_pkg/__init__.py

@@ -0,0 +1,6 @@
+from .b import B
+
+def get_B():
+    return B
+
+B

Lib/test/test_lazy_import/data/cycle_with_load_global_pkg/a.py

@@ -0,0 +1,5 @@
+B = "B"
+
+from .a import get_B
+
+get_B()

Lib/test/test_lazy_import/data/cycle_with_load_global_pkg/b.py

@@ -0,0 +1 @@
+

Lib/test/test_lazy_import/data/metasyntactic/__init__.py

@@ -0,0 +1 @@
+Foo = "Foo"