Fix handling of events declared on the base types of target objects

[AArnott]

Tips for reviewers:

• I changed the existing tests to use a derived type, which caused several to fail.
• I wrapped the existing event enumerating code to do so within an enumeration of the type hierarchy, using exactly the same technique we already used to find methods all the way up the hierarchy. All tests passed after that.

Fixes #340

[codecov-io]

Codecov Report

Merging #341 into master will decrease coverage by 0.29%.
The diff coverage is 62.5%.

@@            Coverage Diff            @@
##           master     #341     +/-   ##
=========================================
- Coverage   87.93%   87.63%   -0.3%     
=========================================
  Files          34       34             
  Lines        2296     2281     -15     
  Branches      445      441      -4     
=========================================
- Hits         2019     1999     -20     
+ Misses        215      214      -1     
- Partials       62       68      +6

Impacted Files	Coverage Δ
src/StreamJsonRpc/JsonRpc.cs	91.3% <62.5%> (-0.75%)	⬇️
src/StreamJsonRpc/Exceptions/RemoteRpcException.cs	33.33% <0%> (-33.34%)	⬇️
...treamJsonRpc/Exceptions/ConnectionLostException.cs	50% <0%> (-25%)	⬇️
src/StreamJsonRpc/ProxyGeneration.cs	97.6% <0%> (-0.35%)	⬇️
src/StreamJsonRpc/WebSocketMessageHandler.cs	100% <0%> (+11.53%)	⬆️

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