Allow plugins without installation procedures

[theboringstuff]

Description

Plugins which do not have installation.procedures cause upgrade failures

File "/usr/local/lib/python3.12/site-packages/kubemarine/thirdparties.py", line 418, in <genexpr>
     for plugin_procedure in plugin_configs['installation']['procedures']
                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
 KeyError: 'procedures'

Solution

Set keys installation and installation.procedures as optional, allowing empty values.

Test Cases

TestCase 1

Steps:

1. Add a custom plugins which does not have installation.procedures sections, run upgrade

Results:

Before	After
Upgrade fails on thirdparties	Upgrade continues

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Integration CI passed
• Unit tests. If Yes list of new/changed tests with brief description
• There is no merge conflicts