Write EventSource events with metadata to EventPipe (dotnet/coreclr#11577)

Write EventSource events with metadata to EventPipe (dotnet/coreclr#11577)

* Fix EventPipe initialization.

* rebase code with master, add prototype of event source metadata

* fix define event

* add null ptr checking

* move WriteEvent metadata serialization to managed side

* Fix enabled keywords for COMPlus_PerformanceTracing=1.

* put parameter name into metadata, use WriteToBuffer

* Write event metadata to the file.

* allocate buffer in EventPipeEvent ctor

* prevent double free

* refactor code

* AddEvent params reorder

Commit migrated from https://github.com/dotnet/coreclr/commit/a7fae647fc09448cce04276a87a2873c09d31d42