Intellij plugin doesn't need IDE restart anymore

[crogoz]

Before this PR

Any update of the palantir-gradle-jdk plugin needed a restart of Intellij.

After this PR

In preparation for #410 (prompting the user to update the version of the plugin), we are making the plugin dynamic (https://plugins.jetbrains.com/docs/intellij/dynamic-plugins.html) such that upgrading the plugin version won't need a restart of the IDE anymore.

==COMMIT_MSG==
Intellij plugin doesn't need IDE restart anymore
==COMMIT_MSG==

Possible downsides?

Not possible to test updating the plugin using ./gradlew runIde. I ran the verification as per https://plugins.jetbrains.com/docs/intellij/dynamic-plugins.html#restrictions & ade sure we are cleaning up all the resources (https://plugins.jetbrains.com/docs/intellij/dynamic-plugins.html#resource-cleanup).

[changelog-app]

Generate changelog in changelog/@unreleased

What do the change types mean?

• feature: A new feature of the service.
• improvement: An incremental improvement in the functionality or operation of the service.
• fix: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way.
• break: Has the potential to break consumers of this service's API, inclusive of both Palantir services
  and external consumers of the service's API (e.g. customer-written software or integrations).
• deprecation: Advertises the intention to remove service functionality without any change to the
  operation of the service itself.
• manualTask: Requires the possibility of manual intervention (running a script, eyeballing configuration,
  performing database surgery, ...) at the time of upgrade for it to succeed.
• migration: A fully automatic upgrade migration task with no engineer input required.

Note: only one type should be chosen.

How are new versions calculated?

• ❗The break and manual task changelog types will result in a major release!
• 🐛 The fix changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease.
• ✨ All others will result in a minor version release.

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

Intellij plugin doesn't need IDE restart anymore

Check the box to generate changelog(s)

• Generate changelog entry

[crogoz]

Previously the user had a button "x" to cancel the background task, but even if they clicked the button nothing would happen until the ./gradle-jdks-setup script finished running.
Now, the button won't be shown anymore.

[autorelease3]

Released 0.49.0