Tech Debt - move entity updater to lbh core

[LBHCallumM]

Summary of changes

Many APIs use this EntityUpdater class, so I have moved it to this shared library.

EntityUpdater is used for patch endpoints, where we want to detect if any changes have been made.

Example usage:

var updaterResponse =  _updater.UpdateEntity<AssetDb, EditAssetAddressDatabase>(existingAsset, requestBody, editAddressRequest.ToDatabase());

if (updaterResponse.NewValues.Any())
{
    await _dynamoDbContext.SaveAsync<AssetDb>(updaterResponse.UpdatedEntity).ConfigureAwait(false);
}

BodyRewindMiddleware is required to get the raw request body (to get around .net serialization limitations)

For example:

var bodyText = await HttpContext.Request.GetRawBodyStringAsync().ConfigureAwait(false);