Py runtime: Move to relative imports #1138

Job	Run time
cpp-lib-build (macos-12, clang, ON)	59s
build (macos-12, tool)	1m 34s
build (macos-12, cpp)	16m 45s
cpp-lib-build (macos-12, clang, OFF)	58s
build (macos-12, csharp)	7m 56s
cpp-lib-build (macos-12, gcc, ON)	59s
build (macos-12, dart)	3m 59s
cpp-lib-build (macos-12, gcc, OFF)	1m 4s
build (macos-12, go)	3m 17s
cpp-lib-build (ubuntu-20.04, clang, ON)	1m 1s
cpp-lib-build (ubuntu-20.04, clang, OFF)	57s
build (macos-12, java)	1m 42s
cpp-lib-build (ubuntu-20.04, gcc, ON)	2m 19s
build (macos-12, javascript)	1m 56s
cpp-lib-build (ubuntu-20.04, gcc, OFF)	2m 31s
build (macos-12, typescript)	12m 3s
cpp-lib-build (windows-2022, clang, ON)	4m 33s
build (macos-12, php)	21m 3s
cpp-lib-build (windows-2022, clang, OFF)	5m 2s
build (macos-12, python3)	1m 49s
cpp-lib-build (windows-2022, cl)	4m 40s
build (ubuntu-20.04, tool)	1m 4s
build (ubuntu-20.04, cpp)	15m 20s
build (ubuntu-20.04, csharp)	5m 29s
build (ubuntu-20.04, dart)	3m 41s
build (ubuntu-20.04, go)	2m 23s
build (ubuntu-20.04, java)	1m 14s
build (ubuntu-20.04, javascript)	1m 27s
build (ubuntu-20.04, typescript)	10m 7s
build (ubuntu-20.04, php)	1m 27s
build (ubuntu-20.04, python3)	1m 36s
build (windows-2022, tool)	1m 46s
build (windows-2022, cpp)	23m 32s
build (windows-2022, csharp)	6m 17s
build (windows-2022, dart)	4m 15s
build (windows-2022, go)	6m 0s
build (windows-2022, java)	2m 6s
build (windows-2022, javascript)	2m 24s
build (windows-2022, typescript)	19m 15s
build (windows-2022, php)	3m 2s
build (windows-2022, python3)	1m 43s
	3h 31m 15s

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