Fix Version.preReleaseIndex

[fthomas]

... and recognize hashes which are only 6 characters long.

preReleaseIndex reported the wrong index for versions with components
with a length greater than one.

This is a follow-up #1549.

[codecov]

Codecov Report

Merging #1552 into master will increase coverage by 0.02%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master    #1552      +/-   ##
==========================================
+ Coverage   70.19%   70.21%   +0.02%     
==========================================
  Files         113      113              
  Lines        1778     1783       +5     
  Branches       59       55       -4     
==========================================
+ Hits         1248     1252       +4     
- Misses        530      531       +1     

Impacted Files	Coverage Δ
...ain/scala/org/scalasteward/core/data/Version.scala	93.58% <87.50%> (-0.94%)	⬇️

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[mzuehlke]

This seems to fix nicely the problems that remained after #1549 👍

[fthomas]

Right, the only remaining problems are updates like these:

• Update coursier to 2.0.0-RC6-23+21-ffe6d4de-SNAPSHOT scalapb/ScalaPB#885: 2.0.0-RC6-21 to 2.0.0-RC6-23+21-ffe6d4de-SNAPSHOT
• Update http4s-core, http4s-dsl to 0.21.6+43-2c1c1172-SNAPSHOT softwaremill/correlator#78: 0.21.0-RC5 to 0.21.6+43-2c1c1172-SNAPSHOT