JNI: avoid enum case record names that collide with enclosing types - #7

Problem

JNI enum extraction capitalizes each Swift case name to generate a nested Java record. That record can have the same name as its enum, another enclosing type, or the generated Case interface. Java rejects these declarations because a nested type cannot share an enclosing type's name.

For example:

public enum Message {
  case message(Int64)
}

Previously, this generated a record named Message inside Message.Case, which fails Java compilation. With this change, the record is named MessageCase, and its payload accessor is consistently named getAsMessageCase():

try (var arena = SwiftArena.ofConfined()) {
    Message value = Message.message(42, arena);
    Message.Case.MessageCase payload = value.getAsMessageCase().orElseThrow();
    long number = payload.arg0(); // 42
}

Changes

• Append Case to a conflicting record name until it differs from every enclosing Swift type name and the generated Case interface.
• Use the resulting name consistently for record declarations, payload accessors, and case dispatch.
• Preserve existing names for cases that do not collide.
• Add generator regressions for enclosing enum names, outer type names, repeated suffixes, and ordinary names, plus Java runtime tests for renamed records and their associated values.

Validation

• Confirmed the collision regression fails against the unmodified generator.
• swift test --disable-experimental-prebuilts --disable-sandbox --filter JNIEnumTests: 11 tests passed.
• ./gradlew :Samples:SwiftJavaExtractJNISampleApp:test --no-daemon: all 287 Java tests passed with no failures or skips, including the new payload round trips.
• swift-format and git diff --check passed.

Tested with Apple Swift 6.4 and JetBrains Runtime 25 on macOS.