minor docfixes in ClusterSingletonManager.scala
=tes #15155 prettyduration should work with infinity
adjust default precision to be 4 (fits use case better)
=act #13964 make BalancingPool mailbox configurable
Merge pull request #2127 from dormidon/3964-unable-to-configure-mailbox-for-routees-under-balancingpool-in-akka-2-3-1

Mailbox configuration for routees under BalancingPool - Issue 3964 fix
=act add one more test to routing.BalancingSpec

see #13964
Merge pull request #15134 from shikhar/patch-1

minor docfixes in ClusterSingletonManager.scala
Merge pull request #15156 from ktoso/tes-pretty-duration-inf

=tes #15155 prettyduration should work with infinity
=pro #15166 do not redefine executeTests
Merge pull request #15177 from 2m/fix-prolonged-mutlijvm-tests

Do not run multi-jvm tests twice
=act #15186 add missing string interpolators

Thanks @retronym for finding these in the logs!

fixes #15186
Merge pull request #15168 from akka/wip-readd-BalancingPool-test-∂π

=act add one more test to routing.BalancingSpec
=pro #15031 separate sbt build file for every module
Merge pull request #15145 from 2m/separate-sbt-files

=pro #15031 separate sbt build file for every module
=act #15165 should fix out-of-bounds in actor creation
Other than that, also improved failure logging when AIOOB happens in the histogram
Added a test which shows why the updateWithExpectedInterval method
should be preferred too.
+act Add japi.Pair and japi.Predicate for streams

(cherry picked from commit 42ce37bb57884c7051d46a1e80b4a4ba4187adf4)

=act Add @SerialVersionUID to japi.Pair

(cherry picked from commit adb2c9bdc20effc84132daaf37e563fb430bf230)
Merge pull request #15169 from ktoso/fix-15165-actor-cration-histogram-OOB

=act #15165 should fix out-of-bounds in actor creation
Merge pull request #15187 from akka/wip-15186-interpolators-∂π

=act #15186 add missing string interpolators
=rem #15109: Separate field in Pass for refuseUid

  - Fixes #15109
  - also fix GotUid race with InvalidAddress supervision event
(cherry picked from commit 3fe83fa)
Merge pull request #15199 from akka/wip-stream-japi-master-patriknw

+act Add japi.Pair and japi.Predicate for streams (for validation)
Merge pull request #15208 from drewhk/wip-15109-refuseuid-clash-fwdport-drewhk

=rem #15109: Separate field in Pass for refuseUid (forward)