fix(webpack): normalize devtool for terser compatibility

[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

Some modules are using #source-map as devtool, this pr is for supporting those modules usage.

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 #6566 into dev will decrease coverage by 0.03%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##              dev    #6566      +/-   ##
==========================================
- Coverage   95.85%   95.82%   -0.04%     
==========================================
  Files          78       78              
  Lines        2705     2709       +4     
  Branches      699      700       +1     
==========================================
+ Hits         2593     2596       +3     
- Misses         97       98       +1     
  Partials       15       15

Flag	Coverage Δ
#e2e	100% <ø> (ø)	⬆️
#fixtures	64.71% <66.66%> (-0.03%)	⬇️
#unit	92.32% <66.66%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
packages/webpack/src/config/base.js	90.47% <66.66%> (-1.61%)	⬇️
packages/vue-renderer/src/renderer.js	94.3% <0%> (+0.81%)	⬆️

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