dvc exp run: Checks out deps and outs of all stages even if not required by stage to run

[schuhschuh]

Bug Report

Description

When executing dvc exp run (with or without --temp, also when specifying --single-item), it checks out all cached deps (and outs?) of stages listed in the dvc.yaml file of the stage specified as target, and also all stages in other dvc.yaml files of other pipelines in the same DVC project.

Reproduce

Expected

Command dvc run exp target should only checkout the data files specified as deps of the target to run, plus maybe all previous stages in the pipeline that produce these if necessary and when --single-item is not specified. Especially when using the --temp option (i.e., --queue + --run-all), this results in a long wait for dvc to check out many data files from unrelated pipelines / stages.

Environment information

Output of dvc version:

$ dvc version
DVC version: 2.0.0a0+273b02
---------------------------------
Platform: Python 3.7.9 on Linux-3.10.0-1127.8.2.el7.x86_64-x86_64-with-centos-7.8.2003-Core
Supports: http, https, s3

Additional Information (if any):