Qdrant: fix skipping upserts

[shawncal]

Description

In the Qdrant connector, during Upsert(), it checks whether the vector already exists in the db; if so, it calls continue and skips upserting. The expected behavior of Upsert() is Insert+Update, but currently only the insert is working updates are explicitly skipped.

Resolves https://github.com/microsoft/semantic-kernel/issues/1035

Also includes some minor cleanup on the internal request builder classes:

• DeleteRange
• UpsertRange ...allow you to create the Builder, add all operations, and Build() in a single statement, so you never have to hold an instance of the Builder as a var just to operate a loop.

Contribution Checklist

• [ ] The code builds clean without any errors or warnings
• [ ] The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
• [ ] The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format
• [ ] All unit tests pass, and I have added new tests where possible
• [ ] I didn't break anyone :smile:

[shawncal]

@tawalke This code is UNTESTED (hence the "Draft" status). Can you please take over this PR, test with a qdrant instance?