ref #6159

* tech(routines): move the async logic from notification to alerting notifier

* tech(notification): reduce code dupe

* fix(notification): dont touch the response unless its an error

* feat(alerting): make alerting exeuction async but flow sync

* tech(alerting): remove commented code

* tech(alerting): remove unused code

* tech(alerting): fix typo

* tech(alerting): implement Context on EvalContext

* tech(alerting): wait for all alerts to return

* feat(alerting): dont allow alert responses to cancel

* Revert "feat(alerting): dont allow alert responses to cancel"

This reverts commit 324b006c96687da18a542942f39c10c99119430c.

* feat(alerting): give alerts some time to finish before closing down

Merge branch 'cloudwatch_interval' of https://github.com/mtanda/grafana into mtanda-cloudwatch_interval

fix(notifications): added form validation and restored Send Test button which was always hidden, #6159

feat(api): fixed minor issue with error message when trying to create duplicate datasource, fixes #6164

fix(migration): fix for sqlstore migration, the execution of the migration and recording of the success of it was not done in same transaction, fixes #5315