Move package edit action close to the target

[danidoni]

Following the conventions used for editing the details of a kiwi image, I've:

• Moved the "Edit Package" button close to the edited details.
• Reimplemented the Cancel button without ajax.
• Fixed some markup issues when saving the modified details

Before

After

Supersedes #10874

Fixes #10510

How to review it:

• Go to a package overview
• Click on the "Edit" button below the package details. The package details get replaced by a form to edit those details.
• Click on Cancel to get the package details back.

Replace this line with a description of your changes. Please follow the suggestions in the comment below.

---

If this PR requires any particular action or consideration before deployment,
please check the reasons or add your own to the list:

• Requires a database migration that can cause downtime. Postpone deployment until maintenance window[1].
• Contains a data migration that can cause temporary inconsistency, so should be run at a specific point of time.
• Changes some configuration files (e.g. options.yml), so the changes have to be applied manually in the reference server.
• A new Feature Toggle[2] should be enabled in the reference server.
• Proper documentation or announcement has to be published upfront since the introduced changes can confuse the users.

[1] https://github.com/openSUSE/open-build-service/wiki/Deployment-of-build.opensuse.org#when-there-are-migrations
[2] https://github.com/openSUSE/open-build-service/wiki/Feature-Toggles-%28Flipper%29#you-want-real-people-to-test-your-feature

[dmarcoux]

It works well. It would be nice to have a transition animation when showing the form after clicking on Edit.

[dmarcoux]

The animation can be in another PR.