D4351: match: improve includematcher.visitchildrenset to be much faster and cached

[spectral (Kyle Lippincott)]

spectral added a comment.


  In https://phab.mercurial-scm.org/D4351#67751, @yuja wrote:
  
  > Can't apply. Can you rebase?
  
  
  Done, sorry for the delay.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D4351

To: spectral, #hg-reviewers
Cc: yuja, durin42, mercurial-devel