refactor: drop getLocalIdent compatibility with webpack@2 and webpack@3

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

Drop compatibility getLocalIdent option with webpack@2 and webpack@3

Breaking Changes

In theory - yes, but loader require webpack@4 and it does not make sense so no

Additional Info

no

[codecov]

Codecov Report

Merging #829 into master will increase coverage by 1.24%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #829      +/-   ##
==========================================
+ Coverage   98.49%   99.74%   +1.24%     
==========================================
  Files          10       10              
  Lines         399      393       -6     
  Branches       96       92       -4     
==========================================
- Hits          393      392       -1     
+ Misses          5        1       -4     
+ Partials        1        0       -1

Impacted Files	Coverage Δ
lib/utils.js	98.21% <100%> (+7.89%)	⬆️

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