Copy module: improve tests allowing to use a managed host which isn't the controller host (#25672)

* set output_dir_expanded using module result

'path' values are expanded using 'expandvars' too

* foo.txt is located in 'files' directory

* Use 'role_path' and 'connection: local' for local paths

'{{ role_path }}/tmp' is used for generated paths

* Use local connection with local paths

/tmp/ansible-test-abs-link and /tmp/ansible-test-abs-link-dir are
defined by targets/copy/files/subdir/subdir1/ansible-test-abs-link
and targets/copy/files/subdir/subdir1/ansible-test-abs-link-dir links.

* task names: add a suffix when same name is reused

* Check that item exists before checking file mode

then error message is more explicit when item doesn't exist

* Use output_dir_expanded only when necessary

* Enforce remote_user when root is required

* Fix remote path

* Use different local & remote user

this is useful when controller and managed hosts are identical

* Checks must not expect output of tested module to be right

* Use a temporary directory on the controller

* Use sha1 & md5 filters instead of hardcoded values

* Use 'remote_dir' for directory on managed host

* Workaround tempfile error on OS X

Error was:
temp_path = tempfile.mkdtemp(prefix='ansible_')
AttributeError: 'module' object has no attribute 'mkdtemp'"

test/integration/targets/copy/defaults/main.yml

@@ -0,0 +1,2 @@
+---
+remote_unprivileged_user: tmp_ansible_test_user