src: precompute field names

[gabrielschulhof]

Field names do not change from row to row, so let's create JS strings only during the process of calling back into JS with the first row, not with each row. We save the JS strings we created while calling back with the first row, and re-use them when creating objects for subsequent rows.

Re: nodejs/abi-stable-node#458

[gabrielschulhof]

select benchmark before and after (ran each 30 times before and 30 times after):

	select
	db.each		db.all
	baseline	this PR	baseline	this PR
	590.95	554.337	726.982	686.921
	577.268	526.597	736.352	665.569
	576.186	536.689	723.251	681.398
	584.32	525.596	724.046	673.034
	592.83	537.028	730.969	689.051
	586.968	555.545	725.337	684.295
	583.011	543.743	729.094	685.417
	579.357	546.343	737.633	675.979
	585.594	526.047	734.532	671.272
	591.169	516.65	726.441	672.008
	581.965	532.032	732.463	668.391
	610.069	531.688	737.95	684.103
	593.087	522.436	738.648	666.182
	590.154	532.068	721.377	673.008
	605.924	519.068	746.159	676.44
	589.368	530.219	716.455	676.914
	582.476	532.27	722.437	681.359
	592.816	508.93	725.039	681.662
	583.031	517.32	712.134	677.893
	628.729	516.115	778.948	664.469
	571.472	539.952	731.096	670.911
	623.705	534.565	773.177	676.954
	578.92	523.784	719.689	677.66
	586.045	538.222	732.234	670.445
	584.54	520.251	719.035	682.739
	571.858	537.804	742.486	680.482
	595.769	521.138	738.136	672.084
	581.354	540.571	715.948	669.942
	580.322	545.146	717.724	668.625
	580.956	521.106	729.451	671.797
average	588.6737667	531.1086667	731.5074333	675.9001333
		▼ 9.78% 👍		▼ 7.60% 👍

[gabrielschulhof]

I don't get why the build fails. node-addon-api requires 16 or 18 or >= 20, and it's getting 18. The version of node should be satisfactory.

[gabrielschulhof]

@daniellockyer can you please help me figure out why the tests are failing?