Add-dependency command updates all manifests

[johnbute]

Add-dependency will update all manifest files in a swift package

Motivation:

#9248

Modifications:

Essentially, just added a function to query all possible manifest files, then apply edits to each one.

Result:

Now, add-dependency can edit multiple manifests at the same time such as swift argument parser.

[johnbute]

There is still needing tests + option to specify the manifest files a user wants to add-dependencies to.

[johnbute]

Furthermore, I think that on top of add-dependency, other similar subcommands, such as add-target and add-product, should also support this logic