Consider adding details and replacements for deprecated comments

[leungyauming]

Some items inside v2ray's codebase are deprecated for years but the comment of those items are not informational.

For example, in app/features/inbound/inbound.go file, the GetRandomInboundProxy function of the Handler struct is deprecated, but the details and the replacements for that functions is not stated, adding difficulties to development.

Please consider adding "Use xxx.xxx instead.' section to the comment of the deprecated items.

[Loyalsoldier]

You can continue working on the PR #553 of mine if you like to.

[leungyauming]

Ok I will take a look first.

[Loyalsoldier]

Any deprecated code should be pushed to branch v5.

[leungyauming]

What do you mean deprecated code should be pushed to branch v5?
Wasn't deprecated code expected to be removed/replaced?

[Loyalsoldier]

Any deprecated code should be removed from branch v5.

[leungyauming]

ok understand