fix: Update Serilog EventLog sink configuration to enable event source creation.

[tippmar-nr]

Enables the manageEventSource parameter on the SeriLog EventLog() sink constructor. This will allow the Agent to attempt to create the New Relic .NET Agent event source on the local machine if it doesn't exist. Note that this attempt will only succeed if the application is running with Administrator privileges. Note that this code is currently applicable only to .NET Framework applications.

If source creation fails, Serilog will catch the exception internally. I've also added a just-in-case try/catch block around the call to configure the EventLog sink. In any case, the Agent will continue to operate, though it will be unable to log to EventLog.

[codecov-commenter]

Codecov Report

Merging #1963 (1d070db) into main (a05dc2a) will decrease coverage by 0.01%.
Report is 1 commits behind head on main.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##             main    #1963      +/-   ##
==========================================
- Coverage   83.58%   83.58%   -0.01%     
==========================================
  Files         402      402              
  Lines       24623    24629       +6     
==========================================
+ Hits        20581    20585       +4     
- Misses       4042     4044       +2     

Files	Coverage Δ
.../NewRelic/Agent/Core/Logging/LoggerBootstrapper.cs	79.87% <83.33%> (-1.22%)	⬇️

... and 3 files with indirect coverage changes