Finished Failover Clustering Notebook and preliminary Availability Group Notebook. (#14339)

* WIP changes

* toc.yml edit

* added first cell to AG page

* Changed to SSMS instructions, will need to change steps.

* switched back to SQL

* added clarification of primary server database requirement.

* fixed spaces

* split adding nodes to its own page.

* more changes

* added message for prerequisites step

* test with invoke command added

* added run direct command to failover cluster notebook

* test-cluster temp file added

* added module change and changed readme

* fixed domain name

* fixed escape

* Test Cluster changed to comment again due to permissions issue

* moved additional failover cluster to first notebook

* more cleanup

* more changes added

* added endpoint url

* fixed commas

* failover cluster wording changed

* added select for sqlvm name

* added a check for service account

* fixed secure password string

* first availability group command added

* Current Availability Group Page

* small change

* configure-ag change

* more changes

* changes made to notebooks

extensions/azurehybridtoolkit/notebooks/hybridbook/_data/toc.yml

@@ -59,6 +59,8 @@
     url: hadr/backup-to-blob
   - title: Create Failover Cluster
     url: hadr/configure-failover
+  - title: Create Availability Group
+    url: hadr/configure-ag
 - title: Offline Migration
   url: /offline-migration/readme
   not_numbered: true