feat(flags): Add LaunchDarkly integration

[aliu39]

Notion doc summarizing our goal, constraints, and potential approaches: https://www.notion.so/sentry/Feature-Flags-JavaScript-SDK-1358b10e4b5d805288abe1a4fede75ed?pvs=4. This PR implements approach 1.

Ref

• https://github.com/getsentry/team-replay/issues/492

[aliu39]

Section added by getsentry/sentry-docs#11746

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
649	2	647	29

View the top 2 failed tests by shortest run time

integrations/featureFlags/launchdarkly/withScope/test.ts Flag evaluations in forked scopes are stored separately.

Stack Traces | 0.195s run time

test.ts:9:11 Flag evaluations in forked scopes are stored separately.

integrations/featureFlags/launchdarkly/basic/test.ts Basic test with eviction, update, and no async tasks

Stack Traces | 0.227s run time

test.ts:8:11 Basic test with eviction, update, and no async tasks

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[HofmannZ]

Will this also work for @launchdarkly/node-server-sdk?

[aliu39]

Will this also work for @launchdarkly/node-server-sdk?

No, because the LDInspectionFlagUsedHandler interface is not available for server side JS. This will work for the other client sdks though (react, node-client)

[HofmannZ]

Will this also work for @launchdarkly/node-server-sdk?

No, because the LDInspectionFlagUsedHandler interface is not available for server side JS. This will work for the other client sdks though (react, node-client)

Ah to bad, we were hoping we could use it with Next.js, but best practice is to use a combination of @launchdarkly/node-server-sdk and launchdarkly-react-client-sdk. (See: https://docs.launchdarkly.com/guides/infrastructure/nextjs).

[billyvg]

aside from the nits, looks pretty good to me