Bug: dm creation and group creation take ~500 milliseconds on Dev

[cameronvoell]

Describe the bug

See re-creation here: #1656

Expected behavior

No response

Steps to reproduce the bug

No response

[cameronvoell]

Initial results on "why does creating a DM take ~450 milliseconds?"

get_membership_update_intent took: 149.325584ms

• load_identity_updates=65.275791ms
• calculate_membership_changes_with_keypackages=82.311ms

sync_with_conn completed in 313.081416ms

• publish_intents succeeded, took: 145.227625ms
  • get_publish_intent_data: 73.69375ms
  • send_group_messages: 70.626667ms
• receive succeeded, took: 77.732417ms
• post_commit succeeded, took: 88.608041ms

Right now the main low hanging fruit I can look at that we seem to be calling get_installation_diff twice, once when constructing the intente for adding the other user to the DM, and then immediately after when publishing the intent. But otherwise no smoking guns here as the time seems evenly distrubuted across 6 discrete actions that are ~70-80ms each:

Function	Related Network Call
load_identity_updates	get_identity_updates_v2
calculate_membership_changes_with_keypackages	get_key_packages_for_installation_ids
(publish_intents) get_publish_intent_data	get_key_packages_for_installation_ids
(publish_intents) send_group_messages	send_group_messages
receive	query_group_messages
post_commit	send_welcome_messages

Next step is to try and remove the extra get_key_packages_for_installation_ids, potentially by implementing a cache for fetching keypackages for installation keys, and then zoom out to see if there is anything else redundant that is occurring.