[7.x] [ci-metrics] unify distributable file count metrics (#76448)

[spalger]

Backports the following commits to 7.x:

• [ci-metrics] unify distributable file count metrics ([ci-metrics] unify distributable file count metrics #76448)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 3802f15

Build metrics

distributable file count

id	value	diff	baseline
default	47126	+47126	-
oss	28913	+28913	-
total	-	-47126	47126
total		+28913

oss distributable file count

id	value	diff	baseline
total	-	-28913	28913

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream