Add JsonRpc.DisplayName property

[AArnott]

This has no functional value at runtime at all. But it will allow the brokered service library to 'name' each JsonRpc object it creates after the concrete type of the descriptor so that when serialization failures occur, it's much easier to backtrace the JsonRpc object to its owning descriptor so we know where to apply the fix.

[Copilot]

Pull request overview

This PR adds a new DisplayName property to the JsonRpc class for improved debugging and diagnostics, allowing developers to assign human-readable names to JsonRpc instances to help trace them back to their creators. The property is purely for diagnostic purposes and doesn't affect RPC functionality.

Changes:

• Adds a new public DisplayName property to JsonRpc class with init accessor for immutable configuration
• Implements DebuggerDisplay attribute to show the display name in debugger views
• Increments version from 2.24 to 2.25 to reflect the new API addition
• Includes a style fix in NerdbankMessagePackFormatter.cs (removes unnecessary this. prefix in nameof)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
version.json	Version bump from 2.24 to 2.25 for new API member
test/StreamJsonRpc.Tests/JsonRpcSimpleTests.cs	New test file with tests for DisplayName property default and settable behaviors
src/StreamJsonRpc/JsonRpc.cs	Adds DisplayName property, DebuggerDisplay attribute, and private DebuggerDisplay property
src/StreamJsonRpc/NerdbankMessagePackFormatter.cs	Style fix: removes unnecessary this. prefix from MemberNotNull attribute

[crmann1]

Just what I needed