feat: Added optional args to logger.log to format string only when log level applies (#706)

## Summary
Message formatting is performance heavy. The logger takes formatted message as a parameter, which means message formatting is being done for all types of logs even in cases when the log level does not apply. This PR adds arguments array to the `log` function to carry token values. Logger already has the functionality to `sprintf` based on extra args if the log level applies. This will increase performance in cases where log level is restricted to more conservative ones such as `ERROR`.

## Test plan
- All Unit tests pass
- Manually tested thoroughly with optimizely-sdk package. A follow up PR for the main package will be created after this is merged and released.

Author: zashraf1985

packages/logging/src/logger.ts

@@ -218,10 +218,10 @@ class OptimizelyLogger implements LoggerFacade {
    * @param {string} [message]
    * @memberof OptimizelyLogger
    */
-  log(level: LogLevel | string, message: string): void {
+  log(level: LogLevel | string, message: string, ...splat: any[]): void {
     this.internalLog(coerceLogLevel(level), {
       message,
-      splat: [],
+      splat,
     })
   }
 

packages/logging/src/models.ts

@@ -22,7 +22,7 @@ export enum LogLevel {
 }
 
 export interface LoggerFacade {
-  log(level: LogLevel | string, message: string): void
+  log(level: LogLevel | string, message: string, ...splat: any[]): void
 
   info(message: string | Error, ...splat: any[]): void
 
@@ -38,5 +38,5 @@ export interface LogManager {
 }
 
 export interface LogHandler {
-  log(level: LogLevel, message: string): void
-}
+  log(level: LogLevel, message: string, ...splat: any[]): void
+}