[improve][build] Disable test retry when running tests in IntelliJ

[lhotari]

Motivation

When running tests in IntelliJ, the current Gradle configuration re-runs failed tests via the testRetryCount system property (default 1). This is undesirable when running tests manually in the IDE: a developer triggering a single test expects to see its actual failure, not a retried run that obscures the original error or flakiness.

IntelliJ delegates test execution to Gradle, and it can be detected at build configuration time via the idea.active system property that IntelliJ sets when invoking Gradle.

Modifications

• build-logic/conventions/src/main/kotlin/pulsar.java-conventions.gradle.kts: when idea.active=true, default testRetryCount to 0 instead of 1. An explicit -PtestRetryCount=... Gradle property still takes precedence.
• tests/integration/build.gradle.kts: same change applied to the integrationTest task.

CLI / CI behavior is unchanged because idea.active is not set there.

Verifying this change

• Make sure that the change passes the CI checks.

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment