SHM: Buffer type API

[yellowhatter]

Describe the feature

We already start getting questions like this:
https://discord.com/channels/914168414178779197/1222489180396064898

From fundamental perspective, I don't like the idea of giving users API to determine the buffer type, as it opens them a way to write configuration-dependent code.

From engineering perspective, it might be useful for some cases if used wisely.
The SHM subsystem is so transparent, that it is not clear for the user if it is properly configured and works.

[yellowhatter]

@Mallets tagging you here