perf: Add startup time benchmarks for the instrumentation sample

[romtsn]

Adds benchmark module to measure the startup time of the instrumentation sample app. It uses the same configuration as has been reported by one of our customers.

Options:

• The benchmark ran on Pixel 3XL
• Minified release build
• Cold Start
• 5 iterations

Results

With Sentry

Without Sentry

Only Sentry block

Which can conclude that on average the SDK adds 20-25ms to the app startup time.

The PR is not meant to be merged and can serve as prior art for the SDK overhead measurement Q2 goal. (Perhaps, we can move this sample app under the sentry-java repo, because it's a bit more complex than the samples there)

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