More idiomatic usage of ConcurrentDictionary

[jnyrup]

Found some places, where we can use built-in ConcurrentDictionary methods to reduce the number of lookups.
It might also improve thread-safety a tad, as currently a value could theoretically be removed/added between calls to ContainsKey and TryGetValue.

I refrained from updating ChromeTargetManager.OnTargetCreated and ChromeTargetManager.OnAttachedToTarget as the valueFactory might be evaluated more than once, to ensure that _targetFactoryFunc is still only evaluated once.

If you call GetOrAdd simultaneously on different threads, valueFactory may be called multiple times, but only one key/value pair will be added to the dictionary.

https://learn.microsoft.com/en-us/dotnet/api/system.collections.concurrent.concurrentdictionary-2.getoradd?view=net-7.0#system-collections-concurrent-concurrentdictionary-2-getoradd(-0-system-func((-0-1)))

[kblok]

Nice findings!