OpenTelemetry docs explain what value Sentry adds

[adinauer]

Description

OTel docs (https://docs.sentry.io/platforms/java/opentelemetry) should explain what value Sentry adds for customers who are already using OpenTelemetry but not Sentry.

See getsentry/sentry-docs#13202 (review) for suggestions on how to improve.

[adinauer]

add an example use case here for when to use the agentless version instead of the agent, like when using GraalVM?

came up here: https://github.com/getsentry/sentry-docs/pull/13202/files/9b1f13ab1e3954095bc40fac9bee841a458f8658#r2043934280