feat(flags): add CTA to flag drawer

[aliu39]

Closes #87149, branched from #87251

Slack screen recording of behavior

Also updates style for inline CTA (issue details "flags" section):

Adds a missing analytics definition, for an event we were emitting from inline CTA 'flags.setup_sidebar_opened'

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
9969	2	9967	4

View the top 2 failed test(s) by shortest run time

EventFeatureFlagList renders nothing if event.contexts.flags is not set and should not show cta - no feature flag

Stack Traces | 0.036s run time

Error: expect(element).not.toBeInTheDocument()

expected document not to contain element, found <h3>Feature Flags</h3> instead
    at Object.<anonymous> (.../events/featureFlags/eventFeatureFlagList.spec.tsx:339:74)

EventFeatureFlagList renders nothing if event.contexts.flags is not set and should not show cta - wrong platform

Stack Traces | 0.049s run time

Error: expect(element).not.toBeInTheDocument()

expected document not to contain element, found <h3>Feature Flags</h3> instead
    at Object.<anonymous> (.../events/featureFlags/eventFeatureFlagList.spec.tsx:312:74)

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[aliu39]

@vuluongj20 suggested this style: https://www.figma.com/design/p2DOzd1RwAHQbq0v6KaYmF/Issue-Details?node-id=5472-35215&t=RbzQjBKLnqGjLaqq-0

[michellewzhang]

does simply group.project not work for project?

Suggested change

	const project = useProjectFromSlug({organization, projectSlug: group.project?.slug});
	const project = group.project;

[michellewzhang]

can any of this file & featureFlagInlineCTA.tsx be refactored into a reusable component?