Texts and thresholds

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The text depends on the distance between the date and now. The texts below are the English ones, which the invariant culture uses too:

var timeProvider = new FakeTimeProvider(new DateTimeOffset(2024, 6, 15, 12, 0, 0, TimeSpan.Zero));
string Format(TimeSpan offset)
{
    var date = RelativeDate.Get(timeProvider.GetUtcNow() + offset, timeProvider);
    return date.ToString(format: null, CultureInfo.InvariantCulture);
}

Assert.Equal("now", Format(TimeSpan.Zero));
Assert.Equal("30 seconds ago", Format(TimeSpan.FromSeconds(-30)));
Assert.Equal("a minute ago", Format(TimeSpan.FromSeconds(-90)));
Assert.Equal("10 minutes ago", Format(TimeSpan.FromMinutes(-10)));
Assert.Equal("an hour ago", Format(TimeSpan.FromMinutes(-50)));
Assert.Equal("5 hours ago", Format(TimeSpan.FromHours(-5)));
Assert.Equal("yesterday", Format(TimeSpan.FromHours(-30)));
Assert.Equal("3 days ago", Format(TimeSpan.FromDays(-3)));
Assert.Equal("one month ago", Format(TimeSpan.FromDays(-45)));
Assert.Equal("3 months ago", Format(TimeSpan.FromDays(-100)));
Assert.Equal("one year ago", Format(TimeSpan.FromDays(-400)));
Assert.Equal("2 years ago", Format(TimeSpan.FromDays(-1000)));

// Dates in the future
Assert.Equal("in 2 hours", Format(TimeSpan.FromHours(2)));
Assert.Equal("tomorrow", Format(TimeSpan.FromHours(30)));
Assert.Equal("in 3 days", Format(TimeSpan.FromDays(3)));

Distance	Past	Future
Exactly 0	`now`
Less than 2 seconds	`one second ago`	`in one second`
2 to 60 seconds	`X seconds ago`	`in X seconds`
1 to 2 minutes	`a minute ago`	`in a minute`
2 to 45 minutes	`X minutes ago`	`in X minutes`
45 to 120 minutes	`an hour ago`	`in an hour`
2 to 24 hours	`X hours ago`	`in X hours`
24 to 48 hours	`yesterday`	`tomorrow`
2 to 30 days	`X days ago`	`in X days`
30 to 60 days	`one month ago`	`in one month`
60 to 365 days	`X months ago`	`in X months`
365 to 730 days	`one year ago`	`in one year`
730 days or more	`X years ago`	`in X years`

The numbers are whole units, rounded down: 90 seconds is a minute ago, and 5 hours and 50 minutes is 5 hours ago.
A month is 30 days and a year is 365 days. The text does not depend on the calendar: yesterday means 24 to 48 hours ago, not the previous calendar day.
The number is formatted with the culture of the text.