[JENKINS-54459] Avoid Angry Jenkins when check now on Plugin Manager (#3718)

* [JENKINS-54459] Avoid angry Jenkins in Plugin Manager. Check Now

* [JENKINS-54459] Avoid angry Jenkins in Plugin Manager. Check Now

* [JENKINS-54459] Fix updateSiteRightJsonTest in Windows

* [JENKINS-54459] Minor fixes

* Avoid deprecated getInstance

Co-Authored-By: MRamonLeon <manuelramonleonjimenez@gmail.com>

* [JENKINS-54459] Some fixes

- Better system properties initialization
- Rename properties
- Localized messages
- Add test for change log level message
- Restore signatureCheck field after test
- Other minor improvements

* [JENKINS-54459] Add Retrier generic class and use it in the checking

* [JENKINS-54459] Improving Spanish messages

* [JENKINS-54459] Fix two javadoc errors

* [JENKINS-54459] Rename constants and its visibility

Rename the constants to do the retries and change their visibilities.

Change the package of the test to be able to access the constants in
order to redefine their values in the tests.

* [JENKINS-54459] Avoid external use of Retrier and test the delay time