Improve FileService Code Coverage

[povolev15]

Add more unit tests to improve code coverage to each class in File Service

1. Checked box without issue indicates False negative for coverage where codacy reports 0% coverage but test exists.
2. Checked box with Issue indicates the associated issue has been addressed.
3. List items in bold represent classes falling below 80% coverage and targeted for improvement

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base

• FileQueryBase [100%]

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CODEC

• FileServiceStateTranslator [100 %]

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HANDLERS

• FileAppendHandler [58 %] #13188
• FileCreateHandler [88 %]
• FileDeleteHandler [77 %] #13189
• FileGetContentsHandler [81 %]
• FileGetInfoHandler [87 %]
• FileHandlers [0%] #13190
• FileSignatureWaiversImpl [0 %] #13191
• FileSystemDeleteHandler [73 %] #13192
• FileSystemUndeleteHandler [71 %] #13193
• FileUpdateHandler [83%]

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SCHEMAS

• InitialModFileGenesisSchema[84 %]

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UTIL

• FileServiceUtils [93 %]

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BASE PACKAGE

• FileServiceImpl [75 %] #13194
• FileStore [100 %]
• ReadableFileStoreImpl [100 %]
• ReadableUpgradeFileStoreImpl [90 %]
• WritableFileStore [87 %]
• WritableUpgradeFileStore [100 %]

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hedera-file-service module

• FileServiceDefinition [0 %] #13729