Backport #22705 by @yp05327
Fixes https://github.com/go-gitea/gitea/issues/22676
Context Data `IsOrganizationMember` and `IsOrganizationOwner` is used to
control the visibility of `people` and `team` tab.
2871ea0809/templates/org/menu.tmpl (L19-L40)
And because of the reuse of user projects page, User Context is changed
to Organization Context. But the value of `IsOrganizationMember` and
`IsOrganizationOwner` are not being given.
I reused func `HandleOrgAssignment` to add them to the ctx, but may have
some unnecessary variables, idk whether it is ok.
I found there is a missing `PageIsViewProjects` at create project page.
Co-authored-by: yp05327 <576951401@qq.com>
