refactor: rename `defaults2.bzl` to `defaults.bzl` #914

Job	Run time
list	26s
workflow (build-unit-tests)	2m 16s
workflow (devkit-core-tests)	1m 23s
workflow (build-cli)	1m 47s
workflow (devkit-core-tests-rerun)	1m 23s
workflow (modules-builder-tests)	1m 56s
	9m 11s

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