Add Linear integration support

[sergeibbb]

Description

Fixes #3991

• Related GKDev issue: Support Linear as an issue tracker in our JS provider library
  • and the library: https://github.com/gitkraken/provider-apis-package-js/pull/238
  • and related Slack conversation
• We need to add full support for all functionality that we have for Jira in order to do so.
• Linear's SDK
• Consider while using Linear SDK:
  • It's always nice if an SDK allows a method of overriding how network requests are made.
  • proper tree shaking

Follow-ups

• some bugfixing: Linear follow-ups #4605

Verification steps

• Connection flow
  
  
• Branch auto link on home
  
• Associate issue with branch
• Start work
  
• Autolinks in inspect
  
  
• Autolinks on commit pop-ups