Should m-p packages re-target to in-support TFMs?

**When libraries were brought over to this repository TFMs were updated to the minimum in-support versions of runtimes**, at that time: `net6.0` and `net462`. Libraries in this repo that target net6.0 are:

- System.Json
- System.Runtime.CompilerServices.Unsafe
- Microsoft.Bcl.Hashcode
- System.Data.SqlClient
- System.Net.WebSockets.WebSocketProtocol
- System.Xml.XPath.XmlDocument

.NET 6 went out-of-support on November 12, 2024 and I wonder if packages in this repository should re-target to the new minimum in-support version: .NET 8. For customers, this would mean that consuming a new version of these packages would raise a warning on out-of-support runtimes.

If doing so, the package's major or minor version should be bumped to communicate the breaking change in respect to semantic versioning.

Start by reviewing the six packages listed in the issue and their targeting and versioning configuration; no files or tests are identified. Determine whether moving from net6.0 to net8.0 is approved, including the semantic-versioning impact, then update the affected package targets and validate the resulting packages.

Written by the indexing model from the issue text.