refactor: e2e test

[XMLHexagram]

This PR is aimed to improve e2e test, related to #1079.

I referenced @ernado's reply in https://github.com/tdlib/td/issues/3083 when implemented this PR.

In this PR, I switch e2e test from server teamgram to telegram official server.

Currently, the account data for e2e testing is exported from a vacant account.

Let me explain how it works.

First, the account credentials used in e2e testing can be exported from tools/export_credentials. These credentials are then stored in the GitHub Environment Secrets. For example, the e2e action now automatically reads the TG_CREDENTIALS variable from the Main environment and uses it for testing.

Finally, owner and maintainers can start e2e testing by commenting /e2e in a PR or by manually triggering the process.

BTW, I set a 3min timeout and 1s interval on e2e test, to reduce rate limit.

I already test this PR in my fork, please check https://github.com/XMLHexagram/tdl/pull/2.

If needed, I can provide an account for testing in tdl.

[iyear]

Thanks! the PR is large, and I’ll take some time to review it later.