Rewrite TimeSpanSource, stop DoubleSource returning infinity

[holonsoftFounder]

The last correctness sweep before the v6.0.0 tag. Both fixes change generated sequences, so they have to land inside the break 6.0 already takes.

TimeSpanSource did not work

Measured against the built library, not read from the code:

new TimeSpanSource()        ->  -10675199.02:48:05.4775808   (every draw, constant)
new TimeSpanSource(1h, 2h)  ->  00:33:31 | 00:53:19 | 00:23:35 | ...
new TimeSpanSource(2h, 1h)  ->  endless loop (killed at 30s, exit 124)

Three separate defects: maxTicks - minTicks overflows long over the default range, the two while loops pull the result out of the range that was asked for, and a reversed range keeps doing ticks *= Random.Next(1, 3) forever. Asking for one to two hours and getting 22 to 58 minutes is the most natural way anyone would use the type.

It picks uniformly from the inclusive tick range now, the same way DateTimeSource does, and throws ArgumentOutOfRangeException on a reversed range. Only ranges symmetric around zero worked before, which is exactly what the old stable-sequence test used, so nothing caught it.

DoubleSource returned infinity

new DoubleSource() gave ∞ on every draw: the default range is the whole range of double and the code computed max - min. DoubleSource, FloatSource and DecimalSource now share the overflow-safe interpolation min * (1 - sample) + max * sample that NumberSource<T> already used. DecimalSource does it in decimal arithmetic instead of the detour through double, so it keeps its full precision:

before: 27879346472004300000000000000
after:  27879346472004256951386422019

RandomIntegerExtensions becomes RandomNumberExtensions and holds both the inclusive integer pick and the continuous one, so NumberSource<T> and the four older sources cannot drift apart again.

Verification

dotnet build -c Release zero warnings, 868 tests per framework on net8/9/10, 2604 total, all green. The stable sequences of TimeSpanSource and FloatSource changed and were regenerated; twelve new tests pin the fixed behaviour, including the three cases above.

🤖 Generated with Claude Code