fix: avoid sharing List values set across samples

[shin4141]

Summary

• Produce a fresh ArrayList for each sample when a List value reaches the set-decomposition fast path.
• Preserve the existing container size and wildcard handling.
• Add regression tests for sample independence and for a fixed-size input list producing a mutable sample.

Reproduction

On main d6e285af401f06a3934e2caddfdad052000276ce, both new tests fail: samples share the supplied list, and removing an item from a sample created from Arrays.asList throws UnsupportedOperationException. This addresses the List examples in #1348.

Tests

• ./gradlew :fixture-monkey:test --tests com.navercorp.fixturemonkey.test.SetCollectionIsolationTest --no-daemon — 2/2 pass after the fix (2/2 failed before).
• ./gradlew :fixture-monkey:test --no-daemon — 1,225/1,225 pass.

Scope

The change covers List values whose declared type accepts ArrayList. Other concrete List types and nested mutable elements are outside this patch.

[CLAassistant]

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