Add SkipLocalsInit attribute

[lahma]

For a very recursive parser what Esprima is, we can reduce overhead by using [SkipLocalsInit]. Performance is better and if test suite is happy, we should be happy.

Some information for reference: https://www.meziantou.net/csharp-9-improve-performance-using-skiplocalsinit.htm

Esprima.Benchmark.FileParsingBenchmark

Diff	Method	FileName	Mean	Error	Gen 0	Gen 1	Allocated
Old	ParseProgram	angular-1.2.5	8.846 ms	0.0354 ms	250.0000	109.3750	4,315 KB
New			8,699.4 μs (-4%)	45.02 μs	250.0000 (0%)	109.3750 (0%)	4,315 KB (0%)
Old	ParseProgram	backbone-1.1.0	1.212 ms	0.0057 ms	41.0156	19.5313	676 KB
New			1,168.8 μs (-6%)	4.02 μs	41.0156 (0%)	19.5313 (0%)	676 KB (0%)
Old	ParseProgram	jquery-1.9.1	6.884 ms	0.0225 ms	226.5625	78.1250	3,764 KB
New			6,931.9 μs (-2%)	36.96 μs	226.5625 (0%)	78.1250 (0%)	3,764 KB (0%)
Old	ParseProgram	jquery.mobile-1.4.2	10.639 ms	0.0467 ms	343.7500	171.8750	5,798 KB
New			10,616.6 μs (-3%)	73.30 μs	343.7500 (0%)	171.8750 (0%)	5,798 KB (0%)
Old	ParseProgram	mootools-1.4.5	5.586 ms	0.0434 ms	187.5000	78.1250	3,091 KB
New			5,562.2 μs (-3%)	33.97 μs	187.5000 (0%)	78.1250 (0%)	3,091 KB (0%)
Old	ParseProgram	underscore-1.5.2	1.022 ms	0.0062 ms	33.2031	13.6719	571 KB
New			994.6 μs (-5%)	4.19 μs	33.2031 (0%)	13.6719 (0%)	571 KB (0%)
Old	ParseProgram	yui-3.12.0	4.965 ms	0.0320 ms	171.8750	70.3125	2,856 KB
New			5,070.9 μs (0%)	26.22 μs	171.8750 (0%)	70.3125 (0%)	2,856 KB (0%)

[adams85]

4-5% perf. gain for adding an attribute. What a catch! 👍