Reduce # of allocated objects

[manodasanW]

• Replace delegates with function pointers where possible
• Remove unnecessary creation of IMarshal object to optimize CreateObject scenario
• Cache subscribe / unsubscribe actions to avoid creating them each time
• Fix some warnings

Before

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
AddAndInvokeMultipleIntEventsToSameEventSource	19,042.9 ns	365.40 ns	406.14 ns	0.4883	0.2136	0.0610	2,649 B
CreateAndIterateList	10,524.33 ns	188.582 ns	251.752 ns	0.7477	0.3662	-	3,144 B

After

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
AddAndInvokeMultipleIntEventsToSameEventSource	18,977.4 ns	363.47 ns	432.69 ns	0.4272	0.1526	0.0305	2,442 B
CreateAndIterateList	9,119.60 ns	174.545 ns	171.427 ns	0.6409	0.3204	-	2,697 B