[JENKINS-74169] Remove onClick handlers in MoPluginConfigView/freeTrialModal.jelly

[shlomomdahan]

requires #9 - to use data-callback in task.jelly

Removes inline onclick handles to comply with CSP.

JENKINS-74169
JENKINS-74171

Testing done

After Changes [74169]
https://github.com/user-attachments/assets/b325c43e-bd08-44d1-9599-960c11bbb661

After Changes [74171]

Screen.Recording.2024-12-06.at.12.27.20.PM.mov

Steps to reproduce [74169]

1. Navigate to Configure global security
2. Under Security Realm, select: miniOrange SAML 2.0 -> then click Apply.
3. Click on the here link -> opens up a page that shows a click here button for free trial.

Steps to reproduce [74171]

1. Navigate to Configure global security
2. Under Security Realm, select: miniOrange SAML 2.0 -> then click Apply.
3. Click on the here link -> opens up a page that shows various config options

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