Update docs for new OpenTelemetry based Sentry

[adinauer]

Description

Update docs for new OpenTelemetry based Sentry:

• new Agent
• can use Agent with Sentry API in application combined
• consider updating manual setup (test manual setup first) or replacing it with using OTel autoconfigure extension
• new modules
  • sentry-opentelemetry-bootstrap
  • sentry-opentelemetry-agentless (also address POTEL 64 - sentry-opentelemetry-agentless module #3961 (comment))
  • sentry-opentelemetry-agentless-spring

[adinauer]

PRs:

• Update platform docs for v8 and use OpenTelemetry sentry-docs#12232
• Update OpenTelemetry docs for Java v8 sentry-docs#12209