Allow CmdDependency set ENV

[cihga39871]

Copying ENV to ENV_ORIGIN when initializing Pipelines.

CmdDependency(; env = [
   prepend_path("PATH", "/bin"; delim = ":"),
   setenv("NEW_VAR", "value")
])

env is some modification of env, but not change env directly.

Modification syntax can be like Modulefile, such as prepend_path, setenv. Since setenv is defined in Julia, we can use another name.

Only pass new env when running Cmd. (setenv)

[cihga39871]

run function can be wrapped in withenv.
Withenv is not thread-safe.