[otlp-transformer] migrate protobuf trace serialization to use hand-rolled implementation

[pichlermarc]

Description

We recently introduced a custom protobuf serializer for Logs, as well as a response deserializer. There were several reasons for this change:

1. performance - a hand-rolled implementation avoids unnecessary transformations, and is therefore quicker and requires fewer allocations.
2. bundle-size - since we need to do fewer transformations, and we don't need the auto-generated code anymore, our bundle size should shrink significantly
3. avoiding protobuf.js production dependency - that dependency is the cause for use of eval is strongly discouraged #4987

This issue tracks implementing trace serialization based on the pattern and and serializer introduced by these two PRs

• feat(otlp-transformer): add custom logs protobuf serializer #6390
• feat(otlp-transformer): add custom logs response deserializer #6530

This issue is considered done when:

• protobuf span serialization is handled using the custom protobuf serializer introduced in feat(otlp-transformer): add custom logs protobuf serializer #6390
• protobuf trace export response is handled using the custom reader introduced in feat(otlp-transformer): add custom logs response deserializer #6530
• auto-generated trace code has been removed from the bundle (adjust protos:generate:* script accordingly as was done in feat(otlp-transformer): add custom logs response deserializer #6530)
• changes have be sufficiently tested
• if [otlp-transformer] migrate protobuf metrics serialization to use hand-rolled implementation #6570 was completed before this issue, also move protobufjs to devDependencies