refactor(rubygems): Extract copystring function to the utils

[zharinov]

Changes

• Extract function to the util/string.ts
• Simplify code by using only slower type of string memory allocation for copy.

Context

• Ref: Change Accept-Encoding for requests to /versions for rubygems.org and set range: bytes=0- #21887

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[renovate-release]

🎉 This PR is included in version 35.97.1 🎉

The release is available on:

• GitHub release
• 35.97.1

Your semantic-release bot 📦🚀