Modernize actions CI

[chapulina]

Update actions style.

[codecov]

Codecov Report

Merging #269 into ign-gazebo2 will increase coverage by 28.77%.
The diff coverage is 78.60%.

@@               Coverage Diff                @@
##           ign-gazebo2     #269       +/-   ##
================================================
+ Coverage        53.78%   82.56%   +28.77%     
================================================
  Files              121      172       +51     
  Lines             5838     9272     +3434     
================================================
+ Hits              3140     7655     +4515     
+ Misses            2698     1617     -1081     

Impacted Files	Coverage Δ
include/ignition/gazebo/Server.hh	100.00% <ø> (ø)
src/systems/breadcrumbs/Breadcrumbs.hh	100.00% <ø> (ø)
src/systems/diff_drive/DiffDrive.hh	100.00% <ø> (ø)
src/systems/joint_controller/JointController.hh	100.00% <ø> (ø)
...stems/joint_state_publisher/JointStatePublisher.hh	100.00% <ø> (ø)
src/systems/physics/Physics.cc	74.12% <ø> (+58.14%)	⬆️
src/systems/user_commands/UserCommands.hh	100.00% <ø> (ø)
src/systems/user_commands/UserCommands.cc	80.32% <16.66%> (ø)
src/systems/battery_plugin/LinearBatteryPlugin.cc	42.08% <20.83%> (ø)
src/gui/GuiRunner.cc	51.42% <50.00%> (+51.42%)	⬆️
... and 103 more

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