Add advanced options to configure certificate checks

[link2xt]

Since options imap_certificate_checks and smtp_certificate_checks were added to the Rust core in deltachat/deltachat-core-rust#647 they need to be added to the Desktop client.

Going to try to do it myself.

[Jikstra]

You probably need to first add the constants to deltachat-node and update the rust core there. Can help you with this, if you want we can also do an audio/video hack session on this.

[link2xt]

I did not any constants to FFI, going to use 0, 1, 2 and 3 for now :)

[r10s]

cmp question at deltachat/deltachat-ios#322

i think it is important to keep the non-power-users in mind. there are tons of self-signed click-hosters eg. here in germany. so we have to choose the defaults very carefully.

i think the idea @hpk42 pointed out somewhere else is reasonable: be lazy on default - but if we know due to the provider-database or by other sources (maybe autoconfigure) that the certificatiate should be good, we should check that.

i do not think it is of much worth to check always and scare the users even before they're really onboarded. i think we do not need this additional ux barrier currently.

[link2xt]

This setting goes into advanced settings, so users who want certificate checking can select "strict" mode. Default option is 0 which means Automatic. Now it means no certificate checks, but in the future it is going to use provider database and can be improved with TOFU.

[pabzm]

This appears to have been implemented, closing it.