Move plugin processing to top of plugins (#6381)

* centralize plugin options

* Centralize plugins options

- move more options to the top
- move validations that depend on options to the top

* use isLoose option

* Move more validations to the top

* Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top

* fix eslint errors

* remove unused parameter

* set default systemGlobal value

* Revert "Move ref parameter for rewriteModuleStatementsAndPrepareHeader() to the top"

This reverts commit b3855302d17fa19d8acb4c8accab3680c8d2710e.

* Revert "Move more validations to the top"

This reverts commit e5861d8a034ff8f553391f55654f753bcf428a5d.

* fix allowMutablePropsOnTags option usage

* improve naming

* change Contructor definition for sake of consistency

* move allowMutablePropsOnTags validation to the top

* add missing !

packages/babel-plugin-transform-es2015-modules-systemjs/src/index.js

@@ -22,7 +22,8 @@ const buildExportAll = template(`
 
 const TYPE_IMPORT = "Import";
 
-export default function({ types: t }) {
+export default function({ types: t }, options) {
+  const { systemGlobal = "System" } = options;
   const IGNORE_REASSIGNMENT_SYMBOL = Symbol();
 
   const reassignmentVisitor = {
@@ -359,7 +360,7 @@ export default function({ types: t }) {
           path.node.body = [
             buildTemplate({
               SYSTEM_REGISTER: t.memberExpression(
-                t.identifier(state.opts.systemGlobal || "System"),
+                t.identifier(systemGlobal),
                 t.identifier("register"),
               ),
               BEFORE_BODY: beforeBody,