Disable breadcrumb disk storage when not required

[robert-smartbear]

Goal

Breadcrumbs are currently stored on disk so that they can be included in OOM and Thermal Kill events.

If these event types are disabled or not supported on the target platform, storage should be disabled to reduce overhead.

Seems particularly important on watchOS.

Changeset

Disable breadcrumb disk storage when not required

Testing

Unit tests

[github-actions]

Bugsnag.framework binary size increased by 184 bytes from 706,776 to 706,960

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.1%    +236  +0.1%    +236    __TEXT,__text
  +0.1%     +96  +0.1%     +96    String Table
  +0.1%     +80  +0.1%     +80    Symbol Table
  +0.5%      +8  +0.5%      +8    Function Start Addresses
  +0.1%      +4  +0.1%      +4    __TEXT,__unwind_info
  [ = ]       0  -1.3%    -184    [__LINKEDIT]
  -1.0%    -240  -1.0%    -240    [__TEXT]
  +0.0%    +184  [ = ]       0    TOTAL

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