ref(onboarding): Split aspnet core onboarding docs

[priscilawebdev]

Contributes to https://linear.app/getsentry/issue/TET-864/introduce-folders-for-onboarding-platforms

[linear]

TET-864 Introduce folders for onboarding platforms

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
12372	1	12371	10

View the top 1 failed test(s) by shortest run time

BalanceChangeAction re-enables form after error

Stack Traces | 1.1s run time

Error: Unable to find an element by: [data-test-id="notes-field"]

Ignored nodes: comments, script, style
...
    at waitForWrapper (.../sentry/node_modules/.pnpm/@[email protected]/node_modules/@.../dom/dist/wait-for.js:163:27)
    at .../sentry/node_modules/.pnpm/@[email protected]/node_modules/@.../dom/dist/query-helpers.js:86:33
    at Object.findByTestId (.../gsAdmin/components/changeBalanceAction.spec.tsx:180:37)
    at runNextTicks (node:internal/process/task_queues:65:5)
    at listOnTimeout (node:internal/timers:549:9)
    at processTimers (node:internal/timers:523:7)

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