refactor: Rename IntegrationTests to Tests and add tests

Move integration test project and assets from FirmwareKit.Sparse.IntegrationTests to FirmwareKit.Sparse.Tests, updating the solution project reference accordingly. Replace the old SparseImageUtilsTests with a new, expanded test file that adds many additional unit/integration cases (CRC, error handling, extraction with CSV mapping, offsets, and edge cases). Update XML documentation/comments in SparseFile.cs and include a small tmpcrc utility project (tmpcrc/Program.cs and csproj). Many test asset files (simg.simg and split parts) were relocated to the new Tests folder.

Signed-off-by: Killy Jack <zicai@openatom.club>

Author: 13584452567