WI #2784 Avoid use of non readonly static fields

[fm-117]

All cases have been corrected except:

• FunctionCallResult.callSiteCounter in StorageArea.cs, line 391
• SecureObjectPool.s_poolUserIdCounter in ImmutableList.cs, line 5727

Both are used to generate unique ids and are legitimate as their only usages are through Intelrocked.Increment(ref int) method which prevent concurrency issues when accessing from multiple threads.

About performance test: the result file was outdated, apparently since 995dda4. Updating it is not strictly part of this issue.

[efr15]

Could you please explain why you remove the static usage of field AntlrPerformanceProfiler in CodeElementsParserStep?

[efr15]

There are still some static fields which are not read-only in projects CodeGen (example: Skeletons.NodeActionsProviderMap) and TypeCobol.Transform.
Maybe we can change them as well.

[fm-117]

Could you please explain why you remove the static usage of field AntlrPerformanceProfiler in CodeElementsParserStep?

Initially the ANTLR stats object was stored on a single static reference which is incorrect because the stats can be computed each time the ANTLR parser is called. Now it is attached to the PerfsStatsForParserInvocation object which is more in-line with its role. It allows to compare stats between first time parsing and last time parsing for example (even though we don't use this for now).

As a drawback the PerfsStatsForParserInvocation object is slightly bigger, holding one more reference. Also, the combination of ANTLR stats is not implemented so the stats won't be available on TotalParsingTime.