Rename all proposal plugins to -proposal- from -transform- (#6570)

packages/babel-plugin-proposal-function-bind/test/fixtures/function-bind/bind/expected.js

@@ -0,0 +1,7 @@
+var _context;
+
+var f = (_context = ctx, ns.obj.func).bind(_context);
+
+var g = (_context = ns.obj).func.bind(_context);
+
+var h = (_context = new X(), y).bind(_context);