CodeGen from PR 15899 in Azure/azure-rest-api-specs

[Hub Generated] Public private branch 'dev-alertsmanagement-Microsoft.AlertsManagement-2021-02-01-preview' (#15899)

* Adds base for updating Microsoft.AlertsManagement from version preview/2019-05-05-preview to version 2021-02-01-preview

* Updates readme

* Updates API version in new specs and examples

* update action rule schema to new api

* fix linter issues

* add alertsmanagement.json

* fix api version

* fix description in targetResource

* match description

* match severity description

* use systemdata type

* run prettier-fix

* change alertsmanagement to latest version

* add integer format

* add x-ms-discriminator-value

* remove summary

* make action polymorphic

* update readme

* prettier fix

* remove space

* add examples

* prettier fix

* fix validation errors

* fix validation errors

* change file name

* update monitor service names

* fix PR comments

* fix description

* change actions to array

* fix prettify issue

* fix lintDiff errors

* rename schedulingConfig to schedule

* fix response codes for put and delete

* fix prettier

* remove query params

* add enabled default value

* rename api version and add severity to conditions

* fix condition enum and remove Z from time in examples

* update conditions, schedule pattern and descriptions

Author: SDKAuto