Use lerna fixed versioning (#523)

Reference: https://github.com/lerna/lerna#fixedlocked-mode-default

1. Currently the SDK create a new tag for each new version each subpackage. This results in having too many tags to maintain.
2. Using independent versioning also adds some unnecessary complexity over the release system.
3. Most popular monorepos use fixed versioning, like Lerna, Babel

This commit does NOT have a conventional commit type
so the tags can be manually created so no version publishing is required.

A tag for v2.2.0 will be created pointing to this release,
for the last published version that was 35a8888

See: aws-sdk-js-v3 switched to fixed versioning with their release candidate in aws/aws-sdk-js-v3#1248

Author: seebees

lerna.json

@@ -1,9 +1,8 @@
 {
-  "lerna": "3.13.3",
   "packages": [
     "modules/*"
   ],
-  "version": "independent",
+  "version": "2.2.0",
   "command": {
     "bootstrap": {
       "nohoist": [