1. Refactor
*   Inheritance: Updated FileCreateTransaction and FileUpdateTransaction to extend ChunkedTransaction instead of the base Transaction class.
*   State Management: Removed redundant local byte[] contents arrays in FileCreate and FileUpdate, migrating state management to the data field provided by ChunkedTransaction.
*   Template Pattern Implementation: Introduced a protected abstract method extractContents(TransactionBody body) in ChunkedTransaction. This allows the base class to handle the generic loop for inner-signed transactions while letting child classes specify which protobuf field to extract content from.

2. Logic Migration
*   Common Logic: Created hasInnerSignedTransactions() and setDataFromInnerSignedTransactions() from FileAppendTransaction chunking logic and moved it to ChunkedTransaction to eliminate code duplication across the three file-service transactions.
*   Chunking Callbacks: Implemented onFreezeChunk overrides in FileCreateTransaction and FileUpdateTransaction. 
*   Added missing import for TransactionID (setFileCreate and setFileUpdate)

3. API Alignment
*   Updated getContents(), setContents(byte[]), and setContents(String) in all target classes to use data field and handlers provided by ChunkedTransaction.
*   Updated initFromTransactionBody() and build() methods to use data field and handlers provided by ChunkedTransaction.