Memory leak in proxy generation

[samolesen]

The interceptor registration creates new ProxyGenerator every time, which means that existing proxies aren't reused. This causes a memory leak. The following line should be changed to be a static instance or registered as a singleton:

foil/src/Foil/ServiceCollectionExtensions.cs

Line 115 in 603ec15

var proxyFactory = new ProxyGenerator();

This has also been an issue in other projects:
Glimpse/Glimpse#126
jacqueskang/IpcServiceFramework#16
corentinaltepe/PerformanceLogger#1