[ENG-6577](https://linear.app/comm/issue/ENG-6577/make-sure-we-use-short-one-time-keys-format).
1. Remove `getOneTimeKeyArray` function.
2. Updates `getOneTimeKeyArray` callsites to `getOneTimeKeyValues`.
3. Remove parsing by offsets from `createSessionAsInitializer`.
4. Remove `keyIndex` argument - it's not used, Identity returns only one one-time key.
5. Rename `oneTimeKeys` -> `oneTimeKey`.
6. Remove calling `getOneTimeKeyValuesFromBlob` - we now expect short keys in session creators.
7. Move parsing long-format to `getOlmSessionInitializationData`. The `get_olm_session_initialization_data` endpoint returns keys in long format, so parse it imediately after receving and in rest of codebase we assume we operate on short format. I decided to not update `get_olm_session_initialization_data` to return short keys as it will be deprecated soon so we can avoid handling backward compatibillity - old clients still expect long format.