Add Gradle Enterprise

[kiview]

Configures the Gradle Enterprise plugin to point at out GE instance and allows CI to push builds.

[kiview]

This is currently failing with:

The response from https://ge.testcontainers.org/scans/publish/gradle/3.6.1/token was not from Gradle Enterprise.
The specified server address may be incorrect, or your network environment may be interfering.

I had the same problem locally at it was related to using Oracle JDK 8 for the Gradle JVM (fixed it by upgrading Gradle JVM to Adopt Open JDK 14, but don't want to do this on CI).

[kiview]

This problem arose from Cloudflare blocking the JDK 8 user agent and we fixed this now in the infrastrucutre.

[kiview]

I did not add the GE key to the CI-Docker-Wormhole pipeline, mainly because the AWS keys also were not there. But we can of course add it later and map the key into the container.

[kiview]

This is supposed to be like this.

[kiview]

From my side, this can be merged to master.

The scans are publicly visible (as they were previously when we used the free service) here:
https://ge.testcontainers.org/scans

This change only reconfigures Gradle build scans for now. Build from authenticated Gradle daemons (in this case, maintainers after executing provisionGradleEnterpriseKeys task or CI) will be published to https://ge.testcontainers.org. If not authenticated, the build will not fail, and simply an info log will be displayed (as can be seen in the case of our wormhole tests):

A build scan was not published as you have not authenticated with server 'ge.testcontainers.org'.

In the future, we can think about conditionally either publishing to GE or the free service, if we ever see the need for this.

This PR does not yet introduce any changes to our build cache.