[wasm][debugger] Fixes exception while debugging on Chrome as IDE

[thaystg]

Fixes this error when trying to debug using chrome as IDE and the BrowserDebugProxy is already started.

fail: DevToolsProxy[0]
      failed: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
         at System.Collections.Generic.Dictionary`2.ValueCollection.Enumerator.MoveNext()
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.OnSourceFileAdded(SessionId sessionId, SourceFile source, ExecutionContext context, CancellationToken token, Boolean resolveBreakpoints)
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.LoadStore(SessionId sessionId, Boolean tryUseDebuggerProtocol, CancellationToken token)
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.LoadStore(SessionId sessionId, Boolean tryUseDebuggerProtocol, CancellationToken token)

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Issue Details

---

Fixes this error when trying to debug using chrome as IDE and the BrowserDebugProxy is already started.

fail: DevToolsProxy[0]
      failed: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
         at System.Collections.Generic.Dictionary`2.ValueCollection.Enumerator.MoveNext()
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.OnSourceFileAdded(SessionId sessionId, SourceFile source, ExecutionContext context, CancellationToken token, Boolean resolveBreakpoints)
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.LoadStore(SessionId sessionId, Boolean tryUseDebuggerProtocol, CancellationToken token)
         at Microsoft.WebAssembly.Diagnostics.MonoProxy.LoadStore(SessionId sessionId, Boolean tryUseDebuggerProtocol, CancellationToken token)

Author:	thaystg
Assignees:	-
Labels:	area-Debugger-mono
Milestone:	-

[thaystg]

/backport to release/8.0-staging

[github-actions]

Started backporting to release/8.0-staging: https://github.com/dotnet/runtime/actions/runs/7756615076