Installing the Nightly MSIX packages, signed with Mozilla's Nightly
key, yields an error: "Error in parsing the app package." Unpacking
with `makeappx.exe` yields:
```
MakeAppx : error: Error info: error 8007000B: The app manifest publisher name (CN=Mozilla Corporation) must match the subject name of the signing certificate (CN=Mozilla Corporation, OU=Firefox Engineering Operations, O=Mozilla Corporation, L=Mountain View, S=California, C=US).
```
Previously, we allowed just the `CN` to vary; in this patch we make
the publisher be the entire publisher subject, and we update the
publisher details in the task definitions.
Differential Revision: https://phabricator.services.mozilla.com/D121896
5bd96bbb60