Drop Java 8 from CI and increase JVM memory

[halotukozak]

Summary

• Remove Java 8 from the GitHub Actions build matrix, making Java 11 the minimum CI version
• Increase JVM max heap from 3G to 8G in .jvmopts

Test plan

• Verify CI passes on Java 11 for all Scala versions (2.13.8, 3.1.2)
• Confirm no jobs reference Java 8

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Updates CI configuration to make Java 11 the minimum JDK used by the main GitHub Actions build workflow, and increases the default JVM heap size used by sbt via .jvmopts.

Changes:

• Remove Java 8 from the build matrix in .github/workflows/build.yml, standardizing jobs on Java 11.
• Update per-job matrix include entries (and the publish job setup-java step) to use Java 11 only.
• Increase default sbt JVM max heap in .jvmopts from 3G to 8G.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.jvmopts	Raises default JVM max heap for sbt invocations.
.github/workflows/build.yml	Drops Java 8 from the main CI workflow build matrix and pins publishing setup-java to 11.

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