some test cleanups & category reorganization (#22010)

* clean up some test categories

* mention exact slice issue

* magics into system

* move trangechecks into overflow

* move tmemory to system

* try fix CI

* try fix CI

* final CI fix

tests/c/tcompile.c

@@ -0,0 +1,3 @@
+int foo(int a, int b) {
+  return a+b;
+}

tests/c/tcompile.nim

@@ -0,0 +1,10 @@
+discard """
+  output: '''44'''
+  joinable: "false"
+"""
+
+{.compile: "tcompile.c".}
+
+proc foo(a, b: cint): cint {.importc: "foo", cdecl.}
+
+echo foo(40, 4)

tests/c/temit.nim

@@ -0,0 +1,15 @@
+discard """
+  output: "509"
+"""
+# Test the new ``emit`` pragma:
+
+{.emit: """
+static int cvariable = 420;
+
+""".}
+
+proc embedsC() =
+  var nimVar = 89
+  {.emit: """printf("%d\n", cvariable + (int)`nimVar`);""".}
+
+embedsC()

tests/c/treservedcidentsasfields.nim

@@ -0,0 +1,39 @@
+discard """
+  targets: "c cpp"
+"""
+
+import macros
+
+macro make_test_type(idents: varargs[untyped]): untyped =
+  result = nnkStmtList.newTree()
+
+  var ident_defs: seq[NimNode] = @[]
+  for i in idents:
+    ident_defs.add newIdentDefs(i, ident("int"))
+
+  result.add newTree(nnkTypeSection,
+    newTree(nnkTypeDef,
+      ident("TestType"),
+      newEmptyNode(),
+      newTree(nnkObjectTy,
+        newEmptyNode(),
+        newEmptyNode(),
+        newTree(nnkRecList,
+          ident_defs
+        )
+      )
+    )
+  )
+
+make_test_type(
+  auto, bool, catch, char, class, compl, const_cast, default, delete, double,
+  dynamic_cast, explicit, extern, false, float, friend, goto, int, long,
+  mutable, namespace, new, operator, private, protected, public, register,
+  reinterpret_cast, restrict, short, signed, sizeof, static_cast, struct, switch,
+  this, throw, true, typedef, typeid, typeof, typename, union, packed, unsigned,
+  virtual, void, volatile, wchar_t, alignas, alignof, constexpr, decltype, nullptr,
+  noexcept, thread_local, static_assert, char16_t, char32_t
+)
+
+# Make sure the type makes it to codegen.
+var test_instance: TestType