CIs: attempt to use csources_v1 (#16282)

* CIs: attempt to use csources_v1
* also updated the BSDs
* also updated azure pipelines
* std modules should not itself use the 'std/' import dir...
* compiler has to be careful with std/ for v1 booting

lib/pure/math.nim

@@ -58,7 +58,7 @@ import std/private/since
 {.push debugger: off.} # the user does not want to trace a part
                        # of the standard library!
 
-import std/[bitops, fenv]
+import bitops, fenv
 
 when defined(c) or defined(cpp):
   proc c_isnan(x: float): bool {.importc: "isnan", header: "<math.h>".}