Add benchmarks project

[gosferano]

Added benchmarks project and set up some initial benchmarks.

Get cached items page

I benchmarked deserialization while using source generators separately and after noticing no substantial improvement got curious what causes requests that are cached to load not so optimally. I suspected it could be due to JsonSerializerOptions getting recomputed for each request. Benchmarked it and it seems about right. Deserialization-only (for the same items page) looks relatively fast.

To benchmark getting cached page with static JsonSerializerOptions I created a new instance inside of WebApiRequest. Used new Connection() and null Gw2Client as parameters for the constructor.

Method	Mean	Error	StdDev	Median	Gen0	Gen1	Gen2	Allocated
GetCachedItemsPage (static JsonSerializerOptions)	6.246 ms	0.1196 ms	0.1119 ms	6.285 ms	277.7778	122.2222	22.2222	1.68 MB
GetCachedItemsPage (recalculated JsonSerializerOptions)	10.44 ms	0.200 ms	0.238 ms	10.38 ms	300.0000	140.0000	20.0000	1.88 MB
DeserializeItemsPage	1.446 ms	0.0236 ms	0.0220 ms	1.442 ms	47.5000	15.0000		291.44 KB

SnakeCaseNamingPolicy.ConvertName benchmark results

In the process had to expose SnakeCaseNamingPolicy. Because of that optimized it a bit (not that it matters a lot) and covered some more valid C# property names. Created some tests for it.

Method	Mean	Error	StdDev	Median	Gen0	Allocated
ConvertConventionalPropertyNameSlow	1,565.9 ns	30.67 ns	43.00 ns	1,571.3 ns	0.3060	1920 B
ConvertConventionalPropertyNameFast	364.1 ns	6.74 ns	7.21 ns	365.3 ns	0.0760	480 B
ConvertUnconventionalPropertyNameSlow	2,672.2 ns	50.24 ns	46.99 ns	2,659.9 ns	0.4820	3024 B
ConvertUnconventionalPropertyNameFast	439.2 ns	8.62 ns	11.20 ns	438.8 ns	0.1120	704 B

Conventional property name used: "HypotheticalPropertyNameWithUnrealisticlyManyWords"

Unconventional property name used: "HyPOThETicAl_PRopeRtYnAmE_wiThUNReAlisTicLyMaNy_wOrDs"