Cleanup legacy models (jaegertracing#6875)

## Which problem is this PR solving?
- Follow-up to jaegertracing#6494

## Description of the changes
- Remove model files that only contained aliases to jaeger-idl types
  - model/*go
  - proto-gen/api_v2/*go
  - thrift-gen/**

## How was this change tested?
- CI

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Signed-off-by: Yuri Shkuro <[email protected]>
Signed-off-by: amol-verma-allen <[email protected]>

Author: yurishkuro