Wrong expected total time in progress bar when make_progress_bar used multiple times

[ctzkane]

Using make_progress_bar multiple times in a WP_CLI command displays wrong expected total time after the first use.

Repro:

Consider the following cli command

class TestMultipleProgressBars {
    private function run($message) {
        $progress = \WP_CLI\Utils\make_progress_bar($message, 10);
        $i = 10;
        while ($i-- >= 0) {
            sleep(1);
            $progress->tick();
        }
        $progress->finish();
        $progress->reset();
        unset($progress);
    }
    public function multiple_progress_bars() {
        $this->run('1st pass');
        $this->run('2nd pass');
        $this->run('3rd pass');
    }
}
WP_CLI::add_command('test', 'TestMultipleProgressBars');

running this results in the following STDOUT output

$ wp test multiple_progress_bars
1st pass  100% [====================================] 0:10 / 0:10
2nd pass  100% [====================================] 0:10 / 0:21
3rd pass  100% [====================================] 0:10 / 0:32

The expected result should read 0:10 as the expected time for the 2nd and 3rd pass. The numbers shown during the execution are also wrong, calculating a much higher time when each subsequent pass starts.

This is due to the usage of static function variables in php-cli-tools lib/cli/Notify.php

	public function speed() {		
              static $tick, $iteration = 0, $speed = 0;

The fix would be to convert those as member variables of the class, or somehow reset them when the Reset method is called.