nest chore: add public api annotation on microservices

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[x] The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
[ ] Tests for the changes have been added (for bug fixes / features)
[ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce?

Issue Number: N/A

Proposal:

Added public api annotation (@publicApi) on microservices, in the following files: - packages/microservices/ctx-host/base-rpc.context.ts - packages/microservices/ctx-host/kafka.context.ts - packages/microservices/ctx-host/mqtt.context.ts - packages/microservices/ctx-host/nats.context.ts - packages/microservices/ctx-host/redis.context.ts - packages/microservices/ctx-host/rmq.context.ts - packages/microservices/ctx-host/tcp.context.ts - packages/microservices/record-builders/mqtt.record-builder.ts - packages/microservices/record-builders/nats.record-builder.ts - packages/microservices/record-builders/rmq.record-builder.ts - packages/microservices/server/server-grpc.ts - packages/microservices/server/server-kafka.ts - packages/microservices/server/server-mqtt.ts - packages/microservices/server/server-nats.ts - packages/microservices/server/server-redis.ts - packages/microservices/server/server-rmq.ts - packages/microservices/server/server-tcp.ts - packages/microservices/server/server.ts