remove TLS 1.1 support for kitkat

[mqus]

• I carefully read the contribution guidelines and agree to them.

partly fixes #2898

I wasn't able to test this yet because I'm not at my usual workstation, the soonest I'll be able to is in ~1 week.

[Redirion]

I don't think that this PR is necessary yet. As you pointed out in your comment #2898 (comment) the browsers will actually drop TLS 1.1 support in March 2020.
See here and here

We should then come back and remove TLS below 1.2 for all devices alltogether.

[TobiGr]

Thanks @mqus.
I agree with @Redirion. We'll postpone this until March and then drop TLS 1.1 completely.

[TobiGr]

It is March. We should be good to go. I plan to merge this at the weekend and leave this open until then for potential comments from other contributors.

[Stypox]

@TobiGr see #2898 (comment)
Is it really useful to disable TLS1.1 on Android 4, while every other user would keep 1.0 and 1.1 enabled? @mqus proposed a solution based on code from another project, maybe we should use that to disable 1.1 everywhere?

[Redirion]

while waiting for the next update for Netcipher this PR could be changed in the following way:
remove the check for Kitkat, to use TLSSocketFactoryCompat for all devices and change ((SSLSocket) socket).setEnabledProtocols(new String[]{"TLSv1.2"}); to ((SSLSocket) socket).setEnabledProtocols(Build.VERSION.SDK_INT > 28 ? new String[]{"TLSv1.2", "TLSv1.3"} : new String[]{"TLSv1.2"});as Android 10 added support for TLSv1.3

[mqus]

Which does not really adress the set ciphersuites, which are also different between android versions. I seriously do not want to touch that, this will have to happen in another PR.

[mqus]

But i agree that waiting for netcipher is not viable.

[Stypox]

At which point is this? Should it be merged now? @Redirion @mqus

[litetex]

Converted to draft:

• no progress/feedback since >9 months.
• no GitHub actions build
• merge conflicts

Should be closed in the future if no further progress happens here.
The only thing keeping it currently open is the fact that this is security related.

[Redirion]

this is superseded by PR #7175