CI, sonic: Replace backend-arm64 docker build with native GHA runner, disable sonic for arm64 (#1794)

* CI: Replace docker amd64 with native runner, switch Docker test arch to amd64

* tests: Remove spaces and new lines from test JSON timestamp fields

* builds: Disable sonic for arm64 due to OKX unmarshal issue

* nits: Improve Dockerfile comment and fix build tag

exchanges/binanceus/binanceus_test.go

@@ -1604,9 +1604,7 @@ var balanceUpdateInputJSON = `
 		"E": 1573200697110,           
 		"a": "BTC",                   
 		"d": "100.00000000",          
-		"T": 1573200697068            
-  }
-}`
+		"T": 1573200697068}}`
 
 func TestWebsocketBalanceUpdate(t *testing.T) {
 	t.Parallel()