Kestrel should select best dev cert and warn if dev cert is out of date

After https://github.com/aspnet/AspNetCore/issues/9810 we now have a new “version” field in the dev certificate. Kestrel needs to ensure it always picks the highest version that it supports when loading dev certificates, just in case multiple versions are available. Also, Kestrel should warn if the highest version it finds is earlier than the version Kestrel expects (as defined by a LatestDevCertVersion constant somewhere, likely in the shared certificate manager code)

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This should be verified on a fresh machine running Windows 10 1903 (check the “About” screen in Windows Settings) and Google Chrome with a process like the following

1. Install 2.2 SDK
2. Create a 2.2 app. Do not include a global.json file
3. dotnet run the app
4. You should get an ERR_SPDY_INADEQUATE_TRANSPORT_SECURITY error. If you don’t, stop here, the issue isn’t reproing properly.
5. Install 3.0 SDK. Do not run dotnet CLI
6. Open the app in Visual Studio 2019
7. Launch the app
8. Verify that at some point in that process, VS prompted you to trust the dev cert.

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We’re pretty sure this is good now.