test: update benchmarks

[jpnurmi]

1. Add native to the existing benchmarks:
   • backend startup
   • SDK init
2. Add new benchmarks parameterized for all backends:
   • scope set tag
   • scope add breadcrumb

See also:

• sentry_set_context opens file handles resulting in hitches #1395
• Native: use IPC instead of flushing to disk where possible #1834

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