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

exchanges/exchange.go

@@ -1,6 +1,7 @@
 package exchange
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net"
@@ -1136,7 +1137,7 @@ func (b *Base) GetSubscriptions() ([]stream.ChannelSubscription, error) {
 }
 
 // AuthenticateWebsocket sends an authentication message to the websocket
-func (b *Base) AuthenticateWebsocket() error {
+func (b *Base) AuthenticateWebsocket(_ context.Context) error {
 	return common.ErrFunctionNotSupported
 }
 
@@ -1354,7 +1355,7 @@ func getURLTypeFromString(ep string) (URL, error) {
 }
 
 // UpdateOrderExecutionLimits updates order execution limits this is overridable
-func (b *Base) UpdateOrderExecutionLimits(a asset.Item) error {
+func (b *Base) UpdateOrderExecutionLimits(_ context.Context, _ asset.Item) error {
 	return common.ErrNotYetImplemented
 }