Remove closure allocation in SerilogLoggerProvider.

[AndreReise]

Addresses #276 issue

BEFORE

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
SerilogOnly	151.4 ns	1.79 ns	1.49 ns	1.00	0.01	0.0381	160 B	1.00
SimpleEvent	255.7 ns	3.38 ns	2.83 ns	1.69	0.02	0.0935	392 B	2.45
Template	343.3 ns	2.84 ns	2.52 ns	2.27	0.03	0.1125	472 B	2.95
StringScope	498.8 ns	3.35 ns	2.97 ns	3.29	0.04	0.2346	984 B	6.15
TemplateScope	699.6 ns	13.36 ns	14.30 ns	4.62	0.10	0.2956	1240 B	7.75
TupleScope	467.8 ns	9.17 ns	8.58 ns	3.09	0.06	0.2217	928 B	5.80
DictionaryScope	513.9 ns	9.06 ns	10.07 ns	3.39	0.07	0.2651	1112 B	6.95
Capturing	654.4 ns	12.32 ns	10.92 ns	4.32	0.08	0.1831	768 B	4.80
CapturingScope	1,069.0 ns	20.69 ns	23.83 ns	7.06	0.17	0.4272	1792 B	11.20
LogInformationScoped	1,112.3 ns	20.53 ns	34.86 ns	7.35	0.24	0.4272	1792 B	11.20
LogInformation_WithEventId	737.1 ns	5.70 ns	4.76 ns	4.87	0.05	0.2422	1016 B	6.35

AFTER

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
SerilogOnly	154.0 ns	2.14 ns	2.00 ns	1.00	0.02	0.0381	160 B	1.00
SimpleEvent	252.2 ns	3.21 ns	3.00 ns	1.64	0.03	0.0858	360 B	2.25
Template	323.3 ns	6.21 ns	7.15 ns	2.10	0.05	0.1049	440 B	2.75
StringScope	492.1 ns	4.44 ns	4.36 ns	3.20	0.05	0.2270	952 B	5.95
TemplateScope	697.9 ns	6.90 ns	5.39 ns	4.53	0.07	0.2880	1208 B	7.55
TupleScope	465.4 ns	7.13 ns	6.32 ns	3.02	0.05	0.2136	896 B	5.60
DictionaryScope	507.4 ns	8.25 ns	7.31 ns	3.30	0.06	0.2575	1080 B	6.75
Capturing	652.8 ns	8.08 ns	6.75 ns	4.24	0.07	0.1755	736 B	4.60
CapturingScope	1,076.7 ns	8.84 ns	7.83 ns	6.99	0.10	0.4196	1760 B	11.00
LogInformationScoped	1,083.3 ns	11.13 ns	8.69 ns	7.04	0.10	0.4196	1760 B	11.00
LogInformation_WithEventId	738.5 ns	11.25 ns	10.52 ns	4.80	0.09	0.2346	984 B	6.15

[nblumhardt]

This looks great, thanks for jumping through all the hoops required for this :-)

Since the logic is now spread between the method and the ScopeCollector helper type, what do you think of making it pull a little more weight, by making the ScopeItems property private, and shifting some more logic into it?

I've sketched a bit of what this might look like, but I didn't give much thought to whether Reverse() could be given a more intent-driven name, or whether the Complete() call might be more like bool TryComplete(out ...), etc.

[nblumhardt]

Thanks @AndreReise 👍