refactor: deprecate cookie field in /vcs.v1.VCSService/GithubLogin and /vcs.v1.VCSService/GithubRefresh

[alsoba13]

Refactor cookie manager and VCS client to use new version of the API:

• refactor: deprecating cookie and start sending token and expirations pyroscope#3573

Changes in VCS client

/vcs.v1.VCSService/GithubLogin and /vcs.v1.VCSService/GithubRefresh now include 3 new fields. Resulting in:

• cookie field becomes deprecated.
• Instead, use token, token_expires_at and refresh_token_expires_at for creating the cookie.

Current cookie format is also deprecated. Backend accepts both the old and the new formats.

New cookie format

Backend expects frontend to append a cookie with the name pyroscope_git_session and the following base64 encoded json body:

• token: the same that came in the backend response (required).
• token_expires_at: optional
• refresh_token_expires_at: optional