fix: use new URL instead of url.parse

[dead-horse]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[Jeff-Tian]

请问一下：https://github.com/eggjs/egg/blob/e7fbd68f32054041b74bc860f11aca05c025c0a9/lib/core/dnscache_httpclient.js

这个缓存刷新机制是啥？

[dead-horse]

egg/lib/core/dnscache_httpclient.js

Line 67 in e7fbd68

if (now - record.timestamp >= this.dnsCacheLookupInterval) {

有过期时间

[codecov]

Codecov Report

Merging #4048 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #4048   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          34      34           
  Lines         947     954    +7     
======================================
+ Hits          947     954    +7

Impacted Files	Coverage Δ
lib/core/dnscache_httpclient.js	100% <100%> (ø)	⬆️
lib/core/utils.js	100% <100%> (ø)	⬆️

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