…eserialization (microsoft#2777)

### Motivation and Context

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All operations inside `WeaviateMemoryStore` whose response models
contain any property of the type `ReadOnlyMemory<>`, will throw an
exception whenever the JSON deserializer tries to deserialize that
specific property.

I believe this is caused by the changes made in
microsoft#2419

### Description

I encountered the following exception while trying out the Weaviate
connector:

```
  System.InvalidOperationException : The type 'System.ReadOnlySpan`1[System.Single]' of property 'Span' on type 'System.ReadOnlyMemory`1[System.Single]' is invalid for serialization or deserialization because it is a pointer type, is a ref struct, or contains generic parameters that have not been replaced by specific types.
  Stack Trace:
     at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_CannotSerializeInvalidType(Type typeToConvert, Type declaringType, MemberInfo memberInfo)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.CreateProperty(Type typeToConvert, MemberInfo memberInfo, JsonSerializerOptions options, Boolean shouldCheckForRequiredKeyword)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.CacheMember(Type typeToConvert, MemberInfo memberInfo, Boolean& propertyOrderSpecified, Dictionary`2& ignoredMembers, Boolean shouldCheckForRequiredKeyword)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.LateAddProperties()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.InitializePropertyCache()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.Configure()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.<EnsureConfigured>g__ConfigureLocked|143_0()
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo.get_JsonTypeInfo()
   at System.Text.Json.ReadStack.Push()
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, TCollection& value)
   at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadFromSpan[TValue](ReadOnlySpan`1 utf8Json, JsonTypeInfo jsonTypeInfo, Nullable`1 actualByteCount)
   at System.Text.Json.JsonSerializer.ReadFromSpan[TValue](ReadOnlySpan`1 json, JsonTypeInfo jsonTypeInfo)
   at System.Text.Json.JsonSerializer.Deserialize[TValue](String json, JsonSerializerOptions options)
   at Microsoft.SemanticKernel.Connectors.Memory.Weaviate.WeaviateMemoryStore.UpsertBatchAsync(String collectionName, IEnumerable`1 records, CancellationToken cancellationToken)+MoveNext() in C:\dotnet\src\Connectors\Connectors.Memory.Weaviate\WeaviateMemoryStore.cs:line 266
```

The `WeaviateMemoryStore` statically instantiates a
`JsonSerializerOptions` object, but without `ReadOnlyMemoryConverter`,
which is required to (de)serialize properties of the `ReadOnlyMemory`
type < .NET 8 (according to the comments inside the converter class).

The issue only occurs whilst deserializing. Serialization works properly
because the responsibility of serialization is abstracted away into
`Microsoft.SemanticKernel.Connectors.Memory.Weaviate.Http.HttpRequest.CreateSerializerOptions()`
-- which does indeed instantiate and passes an instance of
`ReadOnlyMemoryConverter` into the `JsonSerializerOptions`.

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### Contribution Checklist

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- [X] The code builds clean without any errors or warnings
- [X] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [X] All unit tests pass, and I have added new tests where possible
- [X] I didn't break anyone 😄

---------

Co-authored-by: Roger Barreto <19890735+RogerBarreto@users.noreply.github.com>
Co-authored-by: Dmytro Struk <13853051+dmytrostruk@users.noreply.github.com>