Support: Fastify v5

[clarkenciel]

Fastify v5 has changed the signature for custom logger registration.
dd-trace's auto-instrumentation for fastify is now broken for fastify v5.

Here's an example error from our logs:

REDACTED/node_modules/.pnpm/[email protected]/node_modules/fastify/lib/logger.js:84
    throw new FST_ERR_LOG_LOGGER_AND_LOGGER_INSTANCE_PROVIDED()
          ^
FastifyError [Error]: You cannot provide both logger and loggerInstance. Please provide only one.
    at createLogger (REDACTED/node_modules/.pnpm/[email protected]/node_modules/fastify/lib/logger.js:84:11)
    at fastify (REDACTED/node_modules/.pnpm/[email protected]/node_modules/fastify/fastify.js:137:33)
    at fastify (REDACTED/node_modules/.pnpm/[email protected]/node_modules/dd-trace/packages/datadog-instrumentations/src/fastify.js:16:25)
    at fastify (REDACTED/node_modules/.pnpm/[email protected]/node_modules/dd-trace/packages/datadog-shimmer/src/shimmer.js:31:21)
  code: 'FST_ERR_LOG_LOGGER_AND_LOGGER_INSTANCE_PROVIDED',
  statusCode: 500
}

Library versions:
Fastify: 5.0.0
dd-trace: 5.24.0