[AIRFLOW-4364] Allow module names to begin with 0-9 and max 60 chars

[BasPH]

As a result of #5383, it appears it's needed to loosen the restrictions on the module names. This PR allows module names to start with 0-9 and have up to 60 characters.

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-XXX
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.

Description

• Here are some details about my PR, including screenshots of any UI changes:

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

Code Quality

• Passes flake8

[potiuk]

Looks good.

[codecov-io]

Codecov Report

Merging #5391 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5391   +/-   ##
=======================================
  Coverage   79.02%   79.02%           
=======================================
  Files         481      481           
  Lines       30203    30203           
=======================================
  Hits        23868    23868           
  Misses       6335     6335

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