Split Bitbucket Server comments if over max length

[lkysow]

• Refactor the comment split method into a common package

Fixes #280

[codecov]

Codecov Report

Merging #372 into master will decrease coverage by 0.21%.
The diff coverage is 59.37%.

@@            Coverage Diff             @@
##           master     #372      +/-   ##
==========================================
- Coverage   70.51%   70.29%   -0.22%     
==========================================
  Files          61       62       +1     
  Lines        3720     3733      +13     
==========================================
+ Hits         2623     2624       +1     
- Misses        909      921      +12     
  Partials      188      188

Impacted Files	Coverage Δ
server/events/vcs/github_client.go	62.85% <0%> (-10.96%)	⬇️
server/events/vcs/bitbucketserver/client.go	35.82% <0%> (-2.28%)	⬇️
server/events/vcs/common/comment_splitter.go	100% <100%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 387186e...bf19968. Read the comment docs.