Better logging when polling announcements

[Linus045]

When using proxies the logging should be improved to see which proxy is used.
See https://github.com/CyberPunkMetalHead/gateio-crypto-trading-bot-binance-announcements-new-coins/pull/139/files#r799502271

It should also be clear when and what source we are polling announcements from as well as any error that might occur.

As mentioned in the linked comment above, my idea for messages are:

when using proxy: "Getting Binance announcements [Using proxy: 127.0.0.1]"
when no valid proxy exists: "Getting Binance announcements [No proxy available]"
when the proxy feature is disabled: "Getting Binance announcements"

The source "Binance" should be replaced which the one we poll from, e.g. Kucoin/other future sources.