[docs]: Rename/Alias pairs to entries to provide a more intuitive/JS-aligned API

[BioPhoton]

Bug Report

We could rename/alias pairs into entries as it is exactly what the js Object first-class function entries are doing.
As far as is know @benlesh implemented this operator. So maybe he knows best for what reason the naming is why it is.

Also, the source code could be improved as the API changed since it'S implementation and I believe we could go with Object.entries, but maybe this updating of the code should be a separate issue.

I'll wait for feedback here. :)

Furthermore, the description section could be improved compared to the short description section.

Current Behavior
All good!

Reproduction
No bug present

Expected behavior
Behavior is perfect

Possible Solution
Introducing Alias

Additional context/Screenshots

import {of} from 'rxjs';
import {pairs} from 'rxjs/operators';

const obj = {rxjs: 'amazing'};

// JS version
// Output: 
// [rxjs,'amazing']
console.log(Object.entries(obj));

// RxJS version
// Output: 
// [rxjs,'amazing']
of(obj).pipe(pairs()).subscribe(console.log);

[benlesh]

We are deprecating this function and removing it. People can get this by just: from(Object.entries(obj)).