chore: remove entire VM test suite and update test README for CLI-only focus

Delete all VM-related test files including benchmark, call, error, foreign_class, and other API tests, along with their C source, headers, and Wren scripts. Rewrite test/README.md to describe only CLI unit tests and module resolution tests, removing references to VM, compiler, core library, and language semantics tests.

test/module/logical_dir/logical_dir.wren

@@ -0,0 +1,6 @@
+// Import a module from within a named package.
+import "foo/within_foo" for Foo
+// expect: ran foo module
+// expect: ran bar module
+
+System.print(Foo) // expect: from foo

test/module/logical_dir/wren_modules/bar/within_bar.wren

@@ -0,0 +1,5 @@
+// nontest
+var Bar = "from bar"
+System.print("ran bar module")
+
+import "foo/within_foo"

test/module/logical_dir/wren_modules/foo/within_foo.wren

@@ -0,0 +1,5 @@
+// nontest
+var Foo = "from foo"
+System.print("ran foo module")
+
+import "bar/within_bar"

test/module/logical_short/logical_short.wren

@@ -0,0 +1,5 @@
+// Import a module whose name is the same as the package.
+import "foo" for Module
+// expect: ran module
+
+System.print(Module) // expect: from module

test/module/logical_short/wren_modules/foo/foo.wren

@@ -0,0 +1,3 @@
+// nontest
+var Module = "from module"
+System.print("ran module")

test/module/use_nearest_modules_dir/a/b/use_nearest_modules_dir.wren

@@ -0,0 +1,3 @@
+// Stops as soon as it finds a wren_modules directory, regardless of whether or
+// not it contains the desired module.
+import "foo" // expect runtime error: Could not load module 'foo'.

test/module/use_nearest_modules_dir/a/wren_modules/empty.txt

@@ -0,0 +1 @@
+This file exists just to make Git create the containing directory.

test/module/use_nearest_modules_dir/wren_modules/foo/foo.wren

@@ -0,0 +1,2 @@
+// nontest
+System.print("ran foo module")

test/module/walk_up_for_modules_dir/a/b/walk_up_for_modules_dir.wren

@@ -0,0 +1,3 @@
+// Walk up parent directories from the root script to find "wren_modules".
+import "foo"
+// expect: ran foo module

test/module/walk_up_for_modules_dir/wren_modules/foo/foo.wren

@@ -0,0 +1,2 @@
+// nontest
+System.print("ran foo module")