Provide API to customize `client.sdk_info`

[lcian]

Problem Statement

If an SDK is built on top of sentry/sentry-core, it should be possible to customize client.sdk_info to report different information than the default.
We have a use case for this internally for our Vector log sink.
Currently it's already possible to do this in the various before_send hooks but would make sense to be possible to override this on the client if the user wishes to do so.

Solution Brainstorm

Provide a method to set sdk_info on the client.

[linear]

RUST-90 Provide API to customize `client.sdk_info`

[lcian]

Not needed for now by the Vector sink which would have used this, closing.