⬆️ upgrade to dotnet 8

[Odonno]

PR in preparation of .NET 8 release coming this month.

• Upgraded *.csproj to .NET 8
• Use the new JsonNamingPolicy.SnakeCaseLower in .NET 8
• Readme updated
• Update package dependencies to support .NET 8
• Re-run benchmarks to detect performance improvements

New benchmarks results with .NET 8:

Cold Start

Method	Mean	Error	StdDev	Allocated
HttpConstructor	14.54 ms	0.279 ms	0.458 ms	8.63 KB
HttpStaticConstructor	14.12 ms	0.185 ms	0.164 ms	8.89 KB
WsConstructor	2,047.22 ms	8.452 ms	7.906 ms	67.35 KB
WsStaticConstructor	2,046.14 ms	10.143 ms	9.488 ms	67.68 KB

Select

Method	Mean	Error	StdDev	Median	Gen0	Allocated
Http	14,076.6 us	70.86 us	66.28 us	14,059.5 us	-	9.71 KB
HttpWithClientFactory	14,555.9 us	271.67 us	406.62 us	14,432.7 us	-	11.84 KB
WsText	180.1 us	3.03 us	7.31 us	177.4 us	0.7324	13.29 KB

Create

Method	Mean	Error	StdDev	Gen0	Allocated
Http	14,875.5 us	203.81 us	298.74 us	-	53.6 KB
HttpWithClientFactory	14,490.3 us	253.60 us	237.21 us	-	52.79 KB
WsText	305.7 us	6.04 us	8.07 us	2.9297	54.78 KB

Upsert

Method	Mean	Error	StdDev	Gen0	Allocated
Http	14,417.1 us	130.91 us	122.45 us	-	25.29 KB
HttpWithClientFactory	14,394.5 us	126.21 us	111.88 us	-	25.02 KB
WsText	250.4 us	4.72 us	4.42 us	1.4648	26.99 KB

Delete

Method	Mean	Error	StdDev	Gen0	Allocated
Http	14,447.1 us	286.70 us	318.66 us	-	6.16 KB
HttpWithClientFactory	14,260.9 us	162.56 us	126.91 us	-	7.34 KB
WsText	156.9 us	1.45 us	1.29 us	0.2441	7.38 KB

Query

Method	Mean	Error	StdDev	Gen0	Allocated
Http	14,149.2 us	38.42 us	32.08 us	-	13.76 KB
HttpWithClientFactory	14,249.8 us	80.27 us	71.16 us	-	14.8 KB
WsText	288.6 us	5.53 us	6.36 us	0.9766	19.85 KB

Scenario

Method	Mean	Error	StdDev	Gen0	Allocated
Http	177.199 ms	1.6036 ms	1.4216 ms	-	137.57 KB
HttpWithClientFactory	176.810 ms	2.0192 ms	1.6861 ms	-	155.17 KB
WsText	3.864 ms	0.0446 ms	0.0396 ms	7.8125	161.97 KB