Update mill-main to 0.10.15 (#1300) #1305

Job	Run time
bincompat	6m 7s
examples (ubuntu-latest)	5m 8s
integration-tests (ubuntu-20.04)	33m 42s
test (ubuntu-latest, 8, 2.12.17)	5m 23s
examples (windows-latest)	6m 44s
integration-tests (macos-latest)	49m 38s
test (ubuntu-latest, 8, 2.12.18)	4m 38s
integration-tests (windows-latest)	26m 31s
website	3m 47s
test (ubuntu-latest, 8, 2.13.11)	4m 45s
format	14s
test (ubuntu-latest, 8, 2.13.12)	4m 33s
publishLocal	14m 26s
test (ubuntu-latest, 8, 3.3.0)	5m 0s
test (windows-latest, 8, 2.13.12)	5m 28s
test (macos-latest, 8, 2.13.12)	6m 56s
test (ubuntu-latest, 17, 2.12.18)	4m 57s
all-tests	1s
	3h 7m 58s

Provide feedback