PutIndicesSettingsRequestDescriptor ignores IndesSettingsDescriptor when serializing

[dawust]

Elastic.Clients.Elasticsearch version: 8.16.3

Elasticsearch version: 8.11.4

.NET runtime version: 9.0.101

Description of the problem including expected versus actual behavior:
A clear and concise description of what the bug is.

Steps to reproduce:

1. Create a PutIndicesSettingsRequestDescriptor and provide Settings using an IndexSettingsDescriptor
2. Execute PutSettings(Async) with the PutIndicesSettingsRequestDescriptor
3. The request sent to ES is null.

Expected behavior
The given IndexSettingsDescriptor should be respected and serialized

Provide DebugInformation (if relevant):

Only SettingsValue is respected when serializing the PutIndicesSettingsRequestDescriptor. Both SettingsDescriptor and SettingsDescriptorAction seem to be discarded.

	protected override void Serialize(Utf8JsonWriter writer, JsonSerializerOptions options, IElasticsearchClientSettings settings)
	{
		JsonSerializer.Serialize(writer, SettingsValue, options);
	}