Use Lazy for expensive properties in System Dataset

[CaptaiNiveau]

In my tests with repeated creation (clones) of Faker instances, the creation of this dataset was by far the most expensive one. Making it lazy should alleviate a lot of GC pressure, until the Dataset is actually used.

For my benchmark I ran 100 generators in parallel, each of which creating ~100 Fakers. The fakers are cloned from a static base config. A generator has all the configs needed to create all the data needed for our app, which it does.
This should also be reproducible with a simpler setup. That would probably drop the lazy version to even lower allocations as there wouldn't be that much data generated from it.

BenchmarkDotNet v0.13.12, Arch Linux
AMD Ryzen 9 7940HS w/ Radeon 780M Graphics, 1 CPU, 16 logical and 8 physical cores
.NET SDK 8.0.104
  [Host]     : .NET 8.0.4 (8.0.424.16909), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
  DefaultJob : .NET 8.0.4 (8.0.424.16909), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI

Method	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
RunBogusGeneratorInParallel	961.9 ms	18.84 ms	22.43 ms	125000.0000	59000.0000	1000.0000	931.62 MB
RunBogusGeneratorInParallel	309.4 ms	7.10 ms	20.26 ms	21000.0000	7000.0000	1000.0000	154.46 MB

Is there anything that would speak against this change? It speeds up data generation a lot in cases like mine without sacrificing functionality. Tests all passed without issues, too.