sp_BlitzIndex -- Take table creation date into missing index benefit calculation

[BlitzErik]

When we judge missing index benefit, we look at the 'magic benefit number' divided by days of uptime. This makes sense as long as the table has been there the whole time, but less sense if it was created more recently.

We collect create_date in #IndexSanity, which is where we grab missing index details from. To avoid grouping awkwardness, I'm just going to grab ISNULL(NULLIF(MAX(DATEDIFF(DAY, t.create_date, SYSDATETIME())), 0), 1) here, and then in WHERE clause, it will look like

WHERE ( @Mode = 4 AND (magic_benefit_number / CASE WHEN create_days < @DaysUptime THEN create_days ELSE @DaysUptime END) >= 100000 ) 
OR (magic_benefit_number / CASE WHEN create_days < @DaysUptime THEN create_days ELSE @DaysUptime END) >= 100000

[BlitzErik]

There are a couple other places where this calculation lives. Right now, those two places (Table mode and Mode 3) only reference the #MissingIndexes temp table. Will need to think of a clever way to make this match across all outputs.