Camelcase error correlation fields

[robert-smartbear]

Goal

As per discussion, the PD wasn’t showing a consistent name for the span and trace ID fields.

They should now be:
correlation: {traceId: string, spanId: string}

[github-actions]

Bugsnag.framework binary size did not change - 718,312 bytes

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.1%     +15  +0.1%     +15    __TEXT,__cstring
  -0.1%     -15  -0.1%     -15    [__TEXT]
  [ = ]       0  [ = ]       0    TOTAL

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