Plugin Directory welcome string needs proper plural forums

[SergeyBiryukov]

There's a string on the ​Plugin Directory front page:

<strong>%s</strong> plugins with <strong>%s</strong> total downloads are at your fingertips.

It's not localizable due to the lack of _n(). Unless a better option emerges, it should be something like:

printf( __( '%s with %s are at your fingertips' ),
	sprintf( _n( '%s plugin', '%s plugins', $count ), '<strong>' . number_format_i18n( $count ) . '</strong>' ),
	sprintf( _n( '%s total download', '%s total downloads', $downloads ), '<strong>' . number_format_i18n( $downloads ) . '</strong>' ),
);

If we could round the values (39,000+ plugins with 987,841,000+ downloads), that would help too.

Related: #1038

Fixed in [10689-dotorg].

We decided to display the unrounded counts until after the billionth download, at which point we'll change the string once more to simply say something akin to "1+ billion downloads".