EES-5283 Add missing MetaInsertBatchSize app setting to Public API Data Processor function app

[benoutram]

This PR adds a missing app setting AppSettings__MetaInsertBatchSize to the Public API Data Processor function app.

The missing setting is thought to be the cause of data set versions failing to process in Azure environments.

Without this setting we are observing high CPU activity in the ImportMetadata function, thought to be because _appSettingsOptions.MetaInsertBatchSize is resolving to zero in the following block, resulting in the batch iteration to be in an infinite loop.

explore-education-statistics/src/GovUk.Education.ExploreEducationStatistics.Public.Data.Processor/Repository/FilterMetaRepository.cs

Lines 103 to 106 in c52407b

	var batch = options
	.Skip(current)
	.Take(_appSettingsOptions.MetaInsertBatchSize)
	.ToList();

After around 10 minutes (thought to be the function timeout) the exception Npgsql.NpgsqlOperationInProgressException (0x80004005): The connection is already in state 'Executing' was occuring in the following block of code:

explore-education-statistics/src/GovUk.Education.ExploreEducationStatistics.Public.Data.Processor/Repository/FilterMetaRepository.cs

Lines 115 to 125 in c52407b

	var links = await optionTable
	.Where(o =>
	batchRowKeys.Contains(o.Label + ',' + (o.IsAggregate == true ? "True" : "")))
	.OrderBy(o => o.Label)
	.Select((option, index) => new FilterOptionMetaLink
	{
	PublicId = SqidEncoder.Encode(batchStartIndex + index),
	MetaId = meta.Id,
	OptionId = option.Id
	})
	.ToListAsync(token: cancellationToken);

This exception can be reproduced locally by running the function app with AppSettings__MetaInsertBatchSize set to zero.