[master] Workflow updates

[chapulina]

• Add labeler workflow
• Add triage workflow
• Add Ubuntu CI workflow with Codecov upload
• Update badges

---

⚠️ This is using this PR, change to master once that's merged: gazebo-tooling/action-gz-ci#7

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@c14dc67). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #59   +/-   ##
=========================================
  Coverage          ?   14.71%           
=========================================
  Files             ?       13           
  Lines             ?     1318           
  Branches          ?        0           
=========================================
  Hits              ?      194           
  Misses            ?     1124           
  Partials          ?        0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c14dc67...d412c56. Read the comment docs.

[JShep1]

LGTM, I added a small suggestion, are we going to eventually rename bitbucket-pipelines.yml ?

[chapulina]

are we going to eventually rename bitbucket-pipelines.yml ?

Our Jenkins CI still relies on it, so we can't remove it just yet. I ticketed an issue: gazebo-tooling/release-tools#203