fix: Don't mutate passed URL object

[tremby]

Before this change, a passed URL object would be mutated if query parameters were appended via the data option.

Now we clone the object instead, so the original is not affected.

---

Background:

I am passing URL objects to the request method, and then adding query parameters via the data option. Example:

import { request } from "urllib";

const url = new URL("http://example.com");

await request(url, { data: { param1: "value1" } });

I found that if I then make another request to the same URL but with different parameters:

await request(url, { data: { param2: "value2" } });

...a request is actually made to http://example.com?param1=value1&param2=value2.

My URL object is being mutated by the urllib library. I see this as a bug.

[codecov[bot]]

Codecov Report

Merging #470 (5f043e8) into master (8c4ec6c) will increase coverage by 0.00%. Report is 4 commits behind head on master. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #470   +/-   ##
=======================================
  Coverage   99.64%   99.64%           
=======================================
  Files           8        9    +1     
  Lines        1411     1423   +12     
  Branches      253      253           
=======================================
+ Hits         1406     1418   +12     
  Misses          5        5           

Files Changed	Coverage Δ
src/HttpClient.ts	99.57% <100.00%> (+<0.01%)	:arrow_up:

... and 3 files with indirect coverage changes

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[fengmk2]

@tremby Thanks for your patient contribution!