Allow viewing the log file for SelfDiagnostics for .NET Framework

[xiang17]

Fixes Bug#2 in #1689. When running with .NET Framework, the log file cannot be opened as read-only, caused by default FileShare behavior in MemoryMappedFile in .NET Framework.

.NET Framework opens the file in FileShare.None mode but .NET Core opens the file in FileShare.Read mode.

Changes

Use the FileStream version of MemoryMappedFile.CreateFromFile instead of the string version, because the the string version opens the file in different FileShare mode for .NET Framework and .NET Core.

Tested manually:

1. Modify code. Wrap using (var activity = MyActivitySource.StartActivity("SayHello")) block in docs/trace/getting-started/Program.cs with while (true) loop.
2. Create a configurations file and run the project according to issue SelfDiagnosticsModule doesn't filter out logs of lower severity level as configured #1689.
3. When the program is running, open the output file (with name like "getting-started.exe..log"). The file should open successfully.

[codecov]

Codecov Report

Merging #1693 (fe51233) into main (4f39a58) will increase coverage by 0.69%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1693      +/-   ##
==========================================
+ Coverage   82.46%   83.15%   +0.69%     
==========================================
  Files         250      250              
  Lines        6803     6823      +20     
==========================================
+ Hits         5610     5674      +64     
+ Misses       1193     1149      -44     

Impacted Files	Coverage Δ
...nTelemetry/Internal/SelfDiagnosticsConfigParser.cs	81.39% <ø> (+32.55%)	⬆️
...lemetry/Internal/SelfDiagnosticsConfigRefresher.cs	74.52% <100.00%> (+37.31%)	⬆️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	82.35% <0.00%> (+8.82%)	⬆️

[xiang17]

I also ran the unit tests for the code before the fix as a reproduce of the bug. The test cases all passed for .NET Core but failed for .NET Framework as expected.

[cijothomas]

please add this to changelog as well.

[xiang17]

please add this to changelog as well.

Added.

[cijothomas]

@xiang17 please resolve confloicts. change look good for me.

[xiang17]

@xiang17 please resolve confloicts. change look good for me.

Done.