Semconv spec reorg

Context: - https://github.com/open-telemetry/community/issues/3414#issuecomment-4614527035 > Going forward we'll have more examples of federated conventions. We'll probably need a structure like > > ```text > Specs > Semantic Conventions > Core / Common v1.41.1 / ? # current set > GenAI v1.x.y > # Future > Mainframes v1.0.0 > Collector v1.3.2 > Language-specific conventions > Java > ... > How to work with conventions # cross-repo guidance and docs for authors and consumers > External conventions > ``` > > This is probably quite disruptive / involved since we're going to change where the current conventions live. > > Having GenAI on the same level like > > ```text > Specs > Semantic Conventions v1.41.1. # current > Semantic Conventions GenAI v1.x.y > ``` > > would be a solution that's ok now, but we'll need to change it as the list of non-core conventions grows. _Originally posted by @lmolkova in https://github.com/open-telemetry/community/issues/3414#issuecomment-4614527035_