strict effects (#18777)

* fixes #17369
* megatest is green for --cpu:arm64
* docgen output includes more tags/raises
* implemented 'effectsOf' 
* algorithm.nim: uses new effectsOf annotation
* closes #18376
* closes #17475
* closes #13905
* allow effectsOf: [a, b]
* added a test case
* parameters that are not ours cannot be declared as .effectsOf
* documentation
* manual: added the 'sort' example
* bootstrap with the new better options

tests/effects/tstrict_effects2.nim

@@ -0,0 +1,28 @@
+discard """
+  errormsg: "can raise an unlisted exception: Exception"
+  line: 23
+"""
+
+{.push warningAsError[Effect]: on.}
+{.experimental: "strictEffects".}
+
+# bug #13905
+
+proc atoi(v: cstring): cint {.importc: "atoi", cdecl, raises: [].}
+
+type Conv = proc(v: cstring): cint {.cdecl, raises: [].}
+
+var x: Conv = atoi
+
+# bug #17475
+
+type
+  Callback = proc()
+
+proc f(callback: Callback) {.raises: [].} =
+  callback()
+
+proc main =
+  f(proc () = raise newException(IOError, "IO"))
+
+main()