* split global/local/temporary state

There is no way to set custom http headers when making API request to
GitLab.com. This commits adds support for custom headers

test: Add integration specs for chat

See merge request !945



Merged-by: Shekhar Patnaik <spatnaik@gitlab.com>
Approved-by: Shekhar Patnaik <spatnaik@gitlab.com>
Co-authored-by: Pavel Shutsin <pshutsin@gitlab.com>

chore: refactor ai suggestion state

See merge request !949



Merged-by: Shekhar Patnaik <spatnaik@gitlab.com>
Approved-by: Shekhar Patnaik <spatnaik@gitlab.com>
Co-authored-by: Illya <iklymov@gitlab.com>

feat: enable code suggestions by default

See merge request !951



Merged-by: Shekhar Patnaik <spatnaik@gitlab.com>
Approved-by: Shekhar Patnaik <spatnaik@gitlab.com>
Co-authored-by: Kai Armstrong <karmstrong@gitlab.com>

refactor: Add custom http headers support

See merge request !939



Merged-by: Paul Slaughter <pslaughter@gitlab.com>
Approved-by: Paul Slaughter <pslaughter@gitlab.com>
Reviewed-by: Mikołaj Wawrzyniak <mwawrzyniak@gitlab.com>
Co-authored-by: Mikolaj Wawrzyniak <mwawrzyniak@gitlab.com>

feat: introduce promotional banner

See merge request !941



Merged-by: Shekhar Patnaik <spatnaik@gitlab.com>
Approved-by: Shekhar Patnaik <spatnaik@gitlab.com>
Approved-by: Peter Hegman <phegman@gitlab.com>
Reviewed-by: Illya Klymov <xanf@xanf.me>
Reviewed-by: Peter Hegman <phegman@gitlab.com>
Co-authored-by: Illya <iklymov@gitlab.com>