refactor!: move go-chi/session into Gitea (#39504)

The `gitea.com/go-chi/session` package only exists for Gitea, so it
moves into `modules/session` to fix its bugs directly. Fixes the flake
in
https://github.com/go-gitea/gitea/actions/runs/36726154500/job/109923538400.

- Sessions are only written back when changed, so a read-only request
can't revert a concurrent change or restore a logged-out session, like
https://github.com/go-macaron/session/commit/ae808a4a4660c802965c834299ab08f167effd12
- The session cookie is only set once a session holds data
- Every backend refreshes the expiry on load and file sessions are
written atomically
- Also fix  https://github.com/go-gitea/gitea/issues/36176

## ⚠️ BREAKING ⚠️

* the `mysql`, `postgres`, `couchbase` and `memcache` session providers
are removed, use `file`, `db` or `redis` instead
* login-related cookies are renamed to `gitea_session` and
`gitea_remember`, if you'd like to use the old names, set `COOKIE_NAME`
and `COOKIE_REMEMBER_NAME` in app.ini

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

services/context/base_test.go

@@ -21,27 +21,6 @@ func TestMain(m *testing.M) {
 
 func TestRedirect(t *testing.T) {
 	req, _ := http.NewRequest(http.MethodGet, "/", nil)
-
-	cases := []struct {
-		url  string
-		keep bool
-	}{
-		{"http://test", false},
-		{"https://test", false},
-		{"//test", false},
-		{"/://test", true},
-		{"/test", true},
-	}
-	for _, c := range cases {
-		resp := httptest.NewRecorder()
-		b := NewBaseContextForTest(t, resp, req)
-		resp.Header().Add("Set-Cookie", (&http.Cookie{Name: setting.SessionConfig.CookieName, Value: "dummy"}).String())
-		b.Redirect(c.url)
-		has := resp.Header().Get("Set-Cookie") == "i_like_gitea=dummy"
-		assert.Equal(t, c.keep, has, "url = %q", c.url)
-	}
-
-	req, _ = http.NewRequest(http.MethodGet, "/", nil)
 	resp := httptest.NewRecorder()
 	req.Header.Add("X-Gitea-Fetch-Action", "1")
 	b := NewBaseContextForTest(t, resp, req)