[deps] Remove Olm C++ code

[xsanm]

Summary: ENG-11547.

Test Plan:

1. Clean install pods
2. Run yarn cleaninstall
3. Run keyserver & web app
4. Run iOS
5. Run Android

Reviewers: ashoat

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[Ashoat]

Might be good to go through git grep -i olm as part of the test plan

[xsanm]

I ran CI on this in 4eaa727 - it works

Might be good to go through git grep -i olm as part of the test plan

I did that, but we still use olm phrase in many places, like type names, database columns, variables, methods, etc. I reviewed them to make sure anything connected to resources/dependencies is removed