exchanges: Initial context propagation (#744)

* gct: phase one context awareness pass

* exchanges: context propagation pass

* common/requester: force context requirement

* gctcli/exchanges: linter fix

* rpcserver: fix test using dummy rpc server

* backtester: fix comments

* grpc: add correct cancel and timeout for commands

* rpcserver_test: add comment on dummy server

* common: deprecated SendHTTPGetRequest

* linter: fix

* linter: turn on no context check

* apichecker: fix context linter issue

* binance: use param context

* common: remove checks as this gets executed before main

* common: change mutex to RW as clients can be used by multiple go routines.

* common: remove init and JIT default client. Unexport global variables and add protection.

* common: Add comments

* bithumb: after dinner mints fix

engine/subsystem_types.go

@@ -1,6 +1,7 @@
 package engine
 
 import (
+	"context"
 	"errors"
 
 	"github.com/thrasher-corp/gocryptotrader/communications/base"
@@ -54,7 +55,7 @@ type iCommsManager interface {
 type iOrderManager interface {
 	Exists(*order.Detail) bool
 	Add(*order.Detail) error
-	Cancel(*order.Cancel) error
+	Cancel(context.Context, *order.Cancel) error
 	GetByExchangeAndID(string, string) (*order.Detail, error)
 	UpdateExistingOrder(*order.Detail) error
 }