rename case statement macro from match to case (#16923)

* rename case statement macro from match to `case`

* fix test

tests/macros/tcasestmtmacro.nim

@@ -0,0 +1,35 @@
+discard """
+  output: '''
+yes
+'''
+"""
+
+{.experimental: "caseStmtMacros".}
+
+import macros
+
+macro `case`(n: tuple): untyped =
+  result = newTree(nnkIfStmt)
+  let selector = n[0]
+  for i in 1 ..< n.len:
+    let it = n[i]
+    case it.kind
+    of nnkElse, nnkElifBranch, nnkElifExpr, nnkElseExpr:
+      result.add it
+    of nnkOfBranch:
+      for j in 0..it.len-2:
+        let cond = newCall("==", selector, it[j])
+        result.add newTree(nnkElifBranch, cond, it[^1])
+    else:
+      error "custom 'case' for tuple cannot handle this node", it
+
+var correct = false
+
+case ("foo", 78)
+of ("foo", 78):
+  correct = true
+  echo "yes"
+of ("bar", 88): echo "no"
+else: discard
+
+doAssert correct