refactor: move modern detection from server to utils

[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

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 #5584 into dev will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #5584      +/-   ##
==========================================
- Coverage   95.67%   95.63%   -0.04%     
==========================================
  Files          81       81              
  Lines        2636     2635       -1     
  Branches      671      671              
==========================================
- Hits         2522     2520       -2     
- Misses         95       96       +1     
  Partials       19       19

Impacted Files	Coverage Δ
packages/server/src/server.js	97.7% <ø> (-0.08%)	⬇️
packages/utils/src/modern.js	100% <100%> (ø)
packages/webpack/src/builder.js	93.54% <100%> (ø)	⬆️
packages/vue-renderer/src/renderer.js	93.49% <100%> (-0.77%)	⬇️
packages/vue-renderer/src/renderers/spa.js	87.5% <100%> (+0.19%)	⬆️

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[pi0]

Thanks @clarkdo