Add --proxy option to enable the network proxy for the http requests in the android emulator.

Is your feature request related to a problem? Please describe.
Currently, I couldn't set a network proxy for the http requests in the android emulator. I noticed that avd has this option but tns doesnt. And I did all the searching in the documents and stackoverflow and still didnt find one. Currently I am on a project that have to request facebook's api, but I am in China, I cant access those api with proxy in the android emulator, so I am stuck on it now.

Describe the solution you'd like
Add --proxy option to enable the network proxy for the http requests in the android emulator like avd -http-proxy did.

Describe alternatives you've considered
I think --proxy is the most straightforward solution, or u could add some additional file in the project to have this function.

Additional context
I think its a key function, for users in mainland China, without proxy or vpn, they cant access public api from Twitter or Facebook, so please add this function ASAP, thanks.

Beginne damit, den Startpfad des Android-Emulators und die bestehende Optionsanalyse der CLI nachzuverfolgen, wobei das angeforderte Verhalten von --proxy und avd -http-proxy als Referenz dienen. Erledigt ist dies, wenn die Option von der CLI akzeptiert, an die HTTP-Proxy-Konfiguration des Emulators übergeben und mit einer Anfrage des Emulators über einen Proxy verifiziert wird.