Add extra field to log browser extension version

Created by: erzhtor

Closes https://github.com/sourcegraph/sourcegraph/issues/27845.

Description

This PR:

• Adds new version field to log browser extension version for BrowserExtensionConnectedToServer event

How to test

• Run browser extension sg run bext
• Run web locally sg run web-standalone-http
• Open http://localhost:3080/search
• Check DevTools -> Network tab and check BrowserExtensionConnectedToServer event contains version in argument and publicArgument fields

Before merging

• Test on different code hosts (if applicable)

  • GitHub
  • Gitlab
  • GitHub Enterprise
  • Refined GitHub
  • Phabricator
  • Phabricator integration
  • Bitbucket
  • Bitbucket integration

• Test on different browsers (if applicable)

  • Chrome
  • Firefox
  • Safari

• Add change log message to client/browser/CHANGELOG.md, under "Unreleased" section. (if applicable)