Use Android JDK-specific screenshot baselines and adjust graphics screenshot tests

[shai-almog]

Motivation

• The desktop DeviceRunner produces Android screenshots when run on Java SE and needs to compare them against the Android baselines with JDK-specific variants to avoid false mismatches.
• Baselines should live under the existing Android screenshots tree so JDK-specific folders such as 17 and 21 can be used.
• Remove the unused Java SE-specific baseline docs to avoid confusion.

Description

• Updated scripts/run-javase-device-tests.sh to select the baseline directory from scripts/android/screenshots, pick a JDK-aware subdirectory (21 or 17) based on JAVA_VERSION_MAJOR, and allow overriding via CN1SS_ANDROID_BASELINE.
• Kept the CN1 screenshot processing and reporting invocation in place and wire up COMPARE_ENTRIES, COMPARE_JSON, SUMMARY_FILE, and COMMENT_FILE for comparison output.
• Deleted the unused scripts/javase/screenshots/README.md and removed the javase/ mention from scripts/README.md.
• Fixed/cleaned two graphics screenshot tests: removed unused imports and minor formatting in DrawGradient, and corrected fillArc size calculations and added a guard in FillArc to avoid negative widths/heights.

Testing

• No automated tests were executed for this change.

---

Codex Task

[shai-almog]

Android screenshot updates

Compared 30 screenshots: 29 matched, 1 updated.

• graphics-fill-arc — updated screenshot. Screenshot differs (320x640 px, bit depth 8).

  
  Preview info: JPEG preview quality 70; JPEG preview quality 70.
  Full-resolution PNG saved as graphics-fill-arc.png in workflow artifacts.

Native Android coverage

• 📊 Line coverage: 7.15% (3628/50728 lines covered) [HTML preview] (artifact android-coverage-report, jacocoAndroidReport/html/index.html)
  • Other counters: instruction 5.57% (17806/319457), branch 2.72% (847/31083), complexity 3.31% (984/29701), method 5.83% (806/13828), class 9.52% (174/1827)
  • Lowest covered classes
    • kotlin.collections.kotlin.collections.ArraysKt___ArraysKt – 0.00% (0/6327 lines covered)
    • kotlin.collections.unsigned.kotlin.collections.unsigned.UArraysKt___UArraysKt – 0.00% (0/2384 lines covered)
    • org.jacoco.agent.rt.internal_b6258fc.asm.org.jacoco.agent.rt.internal_b6258fc.asm.ClassReader – 0.00% (0/1519 lines covered)
    • kotlin.collections.kotlin.collections.CollectionsKt___CollectionsKt – 0.00% (0/1148 lines covered)
    • org.jacoco.agent.rt.internal_b6258fc.asm.org.jacoco.agent.rt.internal_b6258fc.asm.MethodWriter – 0.00% (0/923 lines covered)
    • kotlin.sequences.kotlin.sequences.SequencesKt___SequencesKt – 0.00% (0/712 lines covered)
    • kotlin.text.kotlin.text.StringsKt___StringsKt – 0.00% (0/623 lines covered)
    • org.jacoco.agent.rt.internal_b6258fc.asm.org.jacoco.agent.rt.internal_b6258fc.asm.Frame – 0.00% (0/564 lines covered)
    • kotlin.collections.kotlin.collections.ArraysKt___ArraysJvmKt – 0.00% (0/495 lines covered)
    • kotlinx.coroutines.kotlinx.coroutines.JobSupport – 0.00% (0/423 lines covered)