<Planning> Codecov platform scale improvement

[rohan-at-sentry]

Develop a plan for the future of the platform.

Goals:

• increased ability to scale to meet the needs of customers
• improved developer experience (many pain points here)
• create paved road for onboarding new products/features
• instrumentation by default

Platform notes doc: https://www.notion.so/sentry/Blue-sky-platform-thoughts-3d102ccb7cf9446ea6dc54bb5c38e937

[trent-codecov]

https://github.com/codecov/internal-issues/issues/459 adding this for consideration on improvements to error handling wrt GH apps