(core) Add installationId to AdminPageConfig and update survey URL

Summary:
This makes the installation ID available on all admin pages, regardless of whether the full edition of Grist is running (previously, the installation ID was read from GristLoadConfig.activation, which is only populated in the full edition).

Fixes a few cases in the UI where the installation ID was undefined (e.g. the help us improve survey).

The survey URL was also updated to point to the correct Grist SaaS instance.

Test Plan: Existing tests

Reviewers: Spoffy

Reviewed By: Spoffy

Differential Revision: https://phab.getgrist.com/D5025