fix(pg): fix instrumentation of ESM-imported pg-pool

[maryliag]

The ESM imported top-level object is a Module Namespace Object per ECMA262 spec that is, apparently, incompatible with the 'PG' class object that 'pg' returns. The ".defaults" holds the equivalent of require('pg').

Fixes: #2759

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.55%. Comparing base (32f41ee) to head (d00650e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2807      +/-   ##
==========================================
+ Coverage   89.50%   89.55%   +0.04%     
==========================================
  Files         180      180              
  Lines        8719     8722       +3     
  Branches     1767     1767              
==========================================
+ Hits         7804     7811       +7     
+ Misses        915      911       -4     

Files with missing lines	Coverage Δ
...elemetry-instrumentation-pg/src/instrumentation.ts	95.04% <100.00%> (+0.07%)	⬆️

... and 1 file with indirect coverage changes

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[pichlermarc]

Thanks for fixing this 🙂
Could you also add a test akin to the below one for pg-pool to avoid regressions?

opentelemetry-js-contrib/plugins/node/opentelemetry-instrumentation-pg/test/pg.test.ts

Lines 1098 to 1125 in d9e757f

	describe('pg (ESM)', () => {
	it('should work with ESM usage', async () => {
	await testUtils.runTestFixture({
	cwd: __dirname,
	argv: ['fixtures/use-pg.mjs'],
	env: {
	NODE_OPTIONS:
	'--experimental-loader=@opentelemetry/instrumentation/hook.mjs',
	NODE_NO_WARNINGS: '1',
	},
	checkResult: (err, stdout, stderr) => {
	assert.ifError(err);
	},
	checkCollector: (collector: testUtils.TestCollector) => {
	const spans = collector.sortedSpans;
	assert.strictEqual(spans.length, 3);
	assert.strictEqual(spans[0].name, 'pg.connect');
	assert.strictEqual(spans[0].kind, 3);
	assert.strictEqual(spans[1].name, 'test-span');
	assert.strictEqual(spans[1].kind, 1);
	assert.strictEqual(spans[2].name, 'pg.query:SELECT otel_pg_database');
	assert.strictEqual(spans[2].kind, 3);
	},
	});
	});
	});

Doing so would also check the box in #1942