ci: compile Kotlin in process for test shards

[ankitTelnyx]

Summary

• keep the established Kotlin daemon path for the normal 8 GiB repository configuration
• switch test shards to in-process Kotlin compilation when generated configuration no longer matches the known 8 GiB baseline
• avoid allocating a second JVM with the same large generated heap

Root cause

PR #216 contains a generated 12 GiB Gradle heap because its larger source tree needs more than 8 GiB to compile. With the default Kotlin daemon strategy, that heap is inherited by a second JVM. This explains the earlier runner shutdowns at 12 GiB and, after #220 capped both JVMs at 8 GiB, the explicit Kotlin java.lang.OutOfMemoryError failures in all three shards.

The conditional keeps current master on its already-proven 8 GiB daemon path. Any non-baseline generated heap fails over to one in-process compiler JVM instead of two competing large JVMs. It does not modify generated SDK source or generated gradle.properties.

Validation

• exact PR release: 6.86.0 #216 head e159f3b77a5f1c6e09ebee4e3164f174bad3a945: clean :telnyx-core:compileKotlin with in-process compilation passed in 9m20s using the branch's 12 GiB setting
• branch-selection probe: master selected normal daemon args; PR release: 6.86.0 #216 selected in-process args
• SDK, ProGuard, and R8 task graph dry-runs passed
• actionlint .github/workflows/ci.yml
• git diff --check