[Experimental] Use System.HashCode instead of JSONConvert.SerializeObject

[LucDeCaf]

This PR replaces the implementations of GetHashCode and Equals for CrudEntry and SyncLocalDatabaseResult, which currently use JSONConvert.SerializeObject followed by a string comparison, with manual implementations relying on System.HashCode and some extra utility functions.

TODO:

• Tests
• Check if [JsonProperty] decorator is still needed on CrudEntry and SyncLocalDatabaseResult

[LucDeCaf]

Update: When checking if we still need the JSON serialisation properties for SyncLocalDatabaseResult, it occurred to me that SyncLocalDatabaseResult isn't actually referenced anywhere, so I removed its definition, and lo and behold, all tests passing. Might be worth checking out.

Edit: There's actually a few classes in Powersync.Common/Client/Sync/Bucket which don't seem to be used. Probably was introduced by #21, since that had a lot of changes/removals.

[Chriztiaan]

Update: When checking if we still need the JSON serialisation properties for SyncLocalDatabaseResult, it occurred to me that SyncLocalDatabaseResult isn't actually referenced anywhere, so I removed its definition, and lo and behold, all tests passing. Might be worth checking out.

Edit: There's actually a few classes in Powersync.Common/Client/Sync/Bucket which don't seem to be used. Probably was introduced by #21, since that had a lot of changes/removals.

Noted. I think it would be good to drop whatever classes we no longer use, and if possible repurpose this PR to have a reference Equals/GetHashCode implementation.