fix: Concatenate telemetry initializer data and method data

[c-owens]

This allows for setting some custom data to be passed in every telemetry request and also in custom properties on track method calls, e.g.:

var telemetryItem = new TelemetryItem()
{
    Tags = new Dictionary<string, object>()
    {
        { "ai.cloud.role", "SPA" },
        { "ai.cloud.roleInstance", "Blazor Wasm" },
    },
    Data = new Dictionary<string, object>
    {
        { "UserName", User?.Name ?? "" },
        { "UserEmail", User?.Email ?? "" },
        { "UserId", User?.UserId ?? Guid.Empty },
    }
};

await appInsights.AddTelemetryInitializer(telemetryItem);

await appInsights.TrackEvent("App Started", new Dictionary<string, object>()
{
    { "EnabledModules", true },
    { "ClientVersion", "1.2.3.4" }
});

Without this change, only UserName, UserEmail, and UserId would be included in the App Started event.

[IvanJosipovic]

Thank you for this fix!

[github-actions]

🎉 This PR is included in version 1.2.1 🎉

The release is available on GitHub release

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