feat(spring): Monitor all @Scheduled methods in Spring Boot 3 - #6275

Part of a series adding automatic Crons monitoring for the most-used job schedulers in each SDK. Check-ins for a monitor that doesn't exist yet are dropped, so today each monitor has to be created by hand with its schedule copied from the code. Sending the job's schedule as the monitor config lets Sentry create the monitor and keep it in sync.

This adds a Spring Boot 3 switch that monitors every @Scheduled method, so methods no longer each need @SentryCheckIn. Off by default.

sentry.monitor-scheduled-tasks=true
# optional: ClassName.methodName, exact or as a regex
sentry.exclude-scheduled-tasks=ReportJobs.sendDailyReport,Internal.*

• The slug is the class and method name in kebab case, e.g. ReportJobs.sendDailyReport becomes report-jobs-send-daily-report. Nested classes include the outer class. Slugs over 50 characters are shortened with a hash suffix so they stay unique.
• The schedule comes from @Scheduled using the logic from feat(spring): Send monitor config from @Scheduled with @SentryCheckIn #6215. Methods whose schedule can't be expressed in the Crons schedule format (fixed delay, several schedules) still check in, without a config.
• Methods with @SentryCheckIn keep their own slug and settings and are not checked in twice.
• Final classes and final methods are skipped, since CGLIB can't proxy them.

Spring Boot 2 and 4 follow in stacked PRs.

Stacked on #6215.