feat(webpack): upgrade terser-webpack-plugin to v2

[clarkdo]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

• Upgrade TerserWebpackPlugin to v2
• Remove sourceMap since TerserWebpackPlugin has better support since v2 https://github.com/webpack-contrib/terser-webpack-plugin/pull/140/files
• Use extractComments condition and remove output.comments

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #6398 into dev will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              dev   #6398      +/-   ##
=========================================
- Coverage   95.61%   95.6%   -0.01%     
=========================================
  Files          79      79              
  Lines        2689    2684       -5     
  Branches      694     692       -2     
=========================================
- Hits         2571    2566       -5     
  Misses        101     101              
  Partials       17      17

Flag	Coverage Δ
#e2e	100% <ø> (ø)	⬆️
#fixtures	50.7% <ø> (-0.1%)	⬇️
#unit	92.28% <ø> (+0.02%)	⬆️

Impacted Files	Coverage Δ
packages/webpack/src/config/base.js	94.68% <ø> (-0.27%)	⬇️

---

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 0e0149d...b7bc666. Read the comment docs.