Airflow: Create SendGridMovedRule to ease upgrade to Airflow 2.0

[turbaszek]

This issue is part of #8765

Rule

Create SendGridMovedRule which corresponds to

SendGrid emailer has been moved

entry in UPDATING.md. This rule should allow users to check if their current configuration needs any adjusting
before migration to Airflow 2.0.

How to guide

To implement a new rule, create a class that inherits from airflow.upgrade.rules.base_rule.BaseRule.
It will be auto-registered and used by airflow upgrade-check command. The custom rule class has to have title,
description properties and should implement check method which returns a list of error messages in case of
incompatibility.

For example:
https://github.com/apache/airflow/blob/ea36166961ca35fc51ddc262ec245590c3e236fb/airflow/upgrade/rules/conn_type_is_not_nullable.py#L25-L42

Remember to open the PR against v1-10-test branch.

[pcandoalmeida]

Hi @turbaszek I'm going to work on this rule also 🙂

[turbaszek]

@pcandoalmeida I assigned you 👏

[turbaszek]

Closed in #11067