[C++] Allow disabling extension type deserialization when reading IPC

[pitrou]

Describe the enhancement requested

Certain users of the IPC format may want to entirely prohibit deserialization of extension types, or adopt a selective whitelist approach when loading extension types.

This may come up useful when there is a concern that some third-party extension types may have latent robusteness issues in their deserialization code.

Component(s)

C++

[AliRana30]

@pitrou I will create a PR for this soon!!

[pitrou]

@AliRana30 I think that the API should be discussed first. I see two main possibilities:

1. a boolean flag (such as bool recreate_extensions = true)
2. an allowlist of allowed extension names (for example a std::optional<std::vector<std::string>> allowed_extensions)

We could be more sophisticated and allow passing a function predicate, but that sounds overkill.

Thoughts @WillAyd @alamb @paleolimbot @lidavidm

[AliRana30]

Apologies for wrong PR and commits.
I will wait for maintainers opinion before creating the new PR.