refactor: moving `labgrid/executor` Python targets to `bazel/labgrid/executor`
The previous target results in a labgrid
import which conflicts with upstream labgrid
module.
This refactor means that the custom manager executor library is imported with bazel.labgrid.executor
.
BREAKING CHANGE: @rules_labgrid//labgrid/executor:manager
is now @rules_labgrid//bazel/labgrid/executor