lib: move encodeStr function to internal for reusable

[ZYSzys]

The encodeStr function and qsEscape function are almost the same.
Extract encodeStr function and move it to internal for reusable.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

cc @mscdex

[mscdex]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/262/

[ZYSzys]

Is the Benchmark CI result acceptable ? 🤔

BTW, didn't understand why we use function

var encode = QueryString.escape;

instead of

var encode = qsEscape;

[mscdex]

BTW, didn't understand why we use function

var encode = QueryString.escape;

instead of

var encode = qsEscape;

The reason is that we allow users to override the escape function.

[mscdex]

Is the Benchmark CI result acceptable ?

I suppose so.

[Trott]

@nodejs/url This doesn't technically need another review, but it would be nice.

[joyeecheung]

CI: https://ci.nodejs.org/job/node-test-pull-request/18695/

[Trott]

Landed in db9a745