Use BigInt instead of Long for the numeric parts of Version

[fthomas]

So we don't have to care about really really long version numbers.

[codecov]

Codecov Report

Merging #579 into master will not change coverage.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master     #579   +/-   ##
=======================================
  Coverage   59.02%   59.02%           
=======================================
  Files          67       67           
  Lines         859      859           
  Branches       41       38    -3     
=======================================
  Hits          507      507           
  Misses        352      352

Impacted Files	Coverage Δ
...in/scala/org/scalasteward/core/model/Version.scala	93.33% <85.71%> (ø)	⬆️

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