[AIRFLOW-5597] Linkify urls in task instance log

[ZxMYS]

#6070 # Jira

• My PR addresses the following [Airflow Jira]
  • https://issues.apache.org/jira/browse/AIRFLOW-5597

Description

• Here are some details about my PR, including screenshots of any UI changes:
  Very often we have urls in our task instances' logs. This change allows these urls to be rendered as clickable links, so users no longer have to copy and paste these urls manually.
  

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
  Just a simple JS change

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":

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.

[codecov-io]

Codecov Report

Merging #6265 into master will increase coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6265      +/-   ##
==========================================
+ Coverage   80.09%   80.28%   +0.19%     
==========================================
  Files         612      612              
  Lines       35320    35320              
==========================================
+ Hits        28289    28357      +68     
+ Misses       7031     6963      -68

Impacted Files	Coverage Δ
airflow/contrib/operators/ssh_operator.py	82.5% <0%> (-1.25%)	⬇️
airflow/utils/dag_processing.py	56.89% <0%> (+0.34%)	⬆️
airflow/gcp/hooks/mlengine.py	78.63% <0%> (+57.26%)	⬆️

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[ZxMYS]

Is there a way to re-run the checks? I don't think the error in travis ci is related to my change.

[mik-laj]

I restarted this Travis's job.

[aoen]

LGTM

[ZxMYS]

To future readers: feel free to improve the regex. The regex in this commit may have been too strict and limiting (e.g. only checks for http / https links, and not allowing Internationalized Domain Names, etc.)