Cleanup ProxyContext logging

• Remove error, warn, debug and trace methods from ProxyContext
• Rewrite code to suppress unnecessary log message computation.

ProxyContext has this logging code:

private final Logger logger = OkapiLogger.get();

public void error(String msg) {
    logger.error(msg);
  }

  public void warn(String msg) {
    logger.warn(msg);
  }

  public void warn(String msg, Throwable e) {
    logger.warn(msg, e);
  }

  public void debug(String msg) {
    logger.debug(msg);
  }

  public void trace(String msg) {
    logger.trace(msg);
  }

This is used by ProxyService, TenantManager, RoutingEntry.

ProxyContext and the other three classes can each create a private static final Logger logger = OkapiLogger.get() and use it directly. There is no need call ProxyContext for logging.

Unnecessary computation should be suppressed using log4j features. Example:

 
pc.debug(prefix + "Validating RoutingEntry " + Json.encode(this));

Log4j lazy lambda evaluation suppresses the JSON encoding if debug log level is disabled:

logger.debug("{} Validating RoutingEntry {}", prefix, () -> Json.encode(this));

The stack trace should be logged by replacing error(message) by error(message, exception).