GenericCopyUtil improvements

[TranceLove]

Description

• Convert to Kotlin for cleaner code
• Removed use of deprecated @Theory in tests
• Not limiting SDK versions, i.e. tests are run on all SDK versions
• Bigger buffer size (1MB) for copy from/to OTG storage to increase robustness

Automatic tests

• Added test cases

Manual tests

• Done

Build tasks success

Successfully running following tasks on local:

• ./gradlew assembledebug
• ./gradlew spotlessCheck

[Copilot]

Pull request overview

This PR modernizes GenericCopyUtil by migrating it (and its tests) from Java to Kotlin, while improving copy robustness/performance via larger transfer quanta and batched progress callbacks. It also replaces deprecated JUnit @Theory-based tests with explicit Kotlin test cases and adds new coverage for cancellation and progress batching.

Changes:

• Replaced GenericCopyUtil Java implementation with a Kotlin version using FileChannel.transferTo for file-to-file copies and batched progress updates.
• Replaced Java unit/instrumentation tests with Kotlin tests (no deprecated @Theory), adding more scenarios (empty file, cancellation, batching).
• Increased transfer buffer quantum (1MB) for OTG/DocumentFile paths and channel-based copies.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
app/src/main/java/com/amaze/filemanager/filesystem/files/GenericCopyUtil.kt	Kotlin rewrite; adds transferTo fast path + progress batching + 1MB transfer quantum.
app/src/main/java/com/amaze/filemanager/filesystem/files/GenericCopyUtil.java	Removes old Java implementation.
app/src/test/java/com/amaze/filemanager/filesystem/files/GenericCopyUtilTest.kt	New Robolectric unit tests replacing @Theory, adding batching/cancellation coverage.
app/src/test/java/com/amaze/filemanager/filesystem/files/GenericCopyUtilTest.java	Removes old Java unit tests.
app/src/androidTest/java/com/amaze/filemanager/filesystem/files/GenericCopyUtilEspressoTest.kt	New instrumented tests in Kotlin, including batching/cancellation scenarios.
app/src/androidTest/java/com/amaze/filemanager/filesystem/files/GenericCopyUtilEspressoTest.java	Removes old Java instrumented tests.

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[Copilot]

FileChannel.transferTo() can legally return 0 even when position < size (e.g., platform/FS limitations). In the current loop this would leave position unchanged and can cause an infinite loop/hang. Add a guard for transferred <= 0 (break + fallback to the ByteBuffer path or throw an IOException) to guarantee progress.