test: modernize JS and tighten equality checking

Checklist

• make -j4 test (UNIX), or vcbuild test nosign (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

Node todo process example with the following test-net-binary.js changes:

var --> const where applicable

==, assert.equal--> ===, assert.strictEqual for all cases