Add support for custom http.agent.

[ghost]

Using custom http.agent has been supported by web3.js and it has some many use cases.

Using proxy-agent for connecting remote nodes via SOCKS5 or HTTP proxy

web3/web3.js#887
web3/web3.js#2827

Using client ssl certiciates for http provider

web3/web3.js#2395

Many npm libraries like axios also supports using custom http.agent as well

https://github.com/axios/axios#request-config

Also, this will help with developers connecting remote nodes with some networking restrictions ( censorship, firewalls, etc ).

Also suggesting to give an ability to use custom user-agent headers to hide information about users.

[ghost]

Hello, what do you think for my proposal? @ricmoo

[ricmoo]

I don't know this will make it into v5, but is certainly a candidate for v6.

I'll move it to the Ideas discussion.