Add sdk.name to events created out of minidumps

[bruno-garcia]

A lot of diagnostics in Sentry are done by looking up sdk.name.
Some of our telemetry internally is also based on that, so we better understand volume of crashes by technology for example.

For example, on Relay we add unreal.crashreporter to events from the unreal endpoint:

relay/relay-server/src/utils/unreal.rs

Line 25 in d12ff53

const CLIENT_SDK_NAME: &str = "unreal.crashreporter";

Suggested SDK name: minidump.
Since it's not "Sentry" specific, we I imagine we don't know what tool created it.

If we know it's breakpad vs crashpad vs other, i'd suggest: minidump.crashpad, minidump.breakpad, minidump.dotnet (dotnet has its own minidump creation for example with support for it's JIT information).