Add net9 target for net tool

[baywet]

Discussed in #5882

^{Originally posted by frodesorhoy December 9, 2024}

TODO:

• add target net 9 to kiota CLI project
• update targets to net9 only for all other projects currently targeting net8
• update GH workflows to install net9
• update ADO pipelines to install net9
• test the artifact being built as similar (content/signature)

[thoekstraorama]

@baywet will there be a prerelease for 1.23.0 with .NET 9 support? Or do we have to wait untill around 6 February for the release?

[baywet]

@thoekstraorama thanks for pointing this out. Preview releases only go out if there are entries under the unreleased section of the changelog. And this was forgotten for this change. I put #6064 to unblock the situation, and the next release should go out on next thursday afternoon EST.

[andrueastman]

@thoekstraorama The preview should be available at https://github.com/microsoft/kiota/releases/tag/v1.23.0-preview.202501310001 and https://www.nuget.org/packages/Microsoft.OpenApi.Kiota/1.23.0-preview.202501300001