Build events tree in the background

[verdie-g]

To avoid blocking the UI. https://github.com/Tewr/BlazorWorker could help.

[verdie-g]

Building the tree only takes a second or two in the worse cases. It appears that the issue is to render the TreeView. Let's see in microsoft/fluentui-blazor#1855 if there is some performance opportunities there.

[verdie-g]

In a future .NET's multi-threading will work in WASM: dotnet/runtime#68162.

[verdie-g]

Since b8a313b it seems like the filtering can take several seconds to execute. So, that filtering could be done in a worker for a better experience. Though, workers have a shared-nothing design, sharing data is only done through message passing. Passing the trace to a worker would mean serializing gigabytes of data.