Introduce API to change DebugSession.name

[isidorn]

We would like to introduce API such that the Extensions can change the name of a DebugSession.
Our proposal is that we make the debugSession.name no longer readonly, but that it can be changed by extensions.

We also thought about constraining the name setter only to the extension which provides the debugger type for this DebugSession but we are not convinced this is needed.

Motivation for this: #79583
PR for hits: #80122

[isidorn]

Tackled via #80122