DoH3 grease setting

[daxpedda]

Is your feature request related to a problem? Please describe.
As a follow-up in #2077 I was looking into how to integrate a configuration that can disable HTTP/3 grease.

Describe the solution you'd like
A setting, preferably in NameServerConfig, that allows HTTP/3 grease to be disabled for specific DNS resolvers.

Describe alternatives you've considered
Alternatively it could be put in ResolverOpts or maybe even in TlsClientConfig, but this setting is actually unrelated to TLS.

Additional context
The reason why I thought this might require some discussion is that this is just a workaround for a bug, see hyperium/h3#206. So it might not be desirable to add this setting at all.

There might be better case for putting it into ResolverOpts, because AFAIK the only reason why anybody would like to disable grease, apart from circumventing bugs, is to save on a couple of bytes. So it might make more sense to make it a less specific (compared to NameServerConfig) setting.