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.go

@@ -149,16 +149,6 @@ func (b *Base) PlainText(status int, text string) {
 // Redirect redirects the request
 func (b *Base) Redirect(location string, status ...int) {
 	code := util.OptionalArg(status, http.StatusSeeOther)
-
-	if !httplib.IsRelativeURL(location) {
-		// Some browsers (Safari) have buggy behavior for Cookie + Cache + External Redirection, eg: /my-path => https://other/path
-		// 1. the first request to "/my-path" contains cookie
-		// 2. some time later, the request to "/my-path" doesn't contain cookie (caused by Prevent web tracking)
-		// 3. Gitea's Sessioner doesn't see the session cookie, so it generates a new session id, and returns it to browser
-		// 4. then the browser accepts the empty session, then the user is logged out
-		// So in this case, we should remove the session cookie from the response header
-		removeSessionCookieHeader(b.Resp)
-	}
 	// In case the request is made by "fetch-action" module, make JS redirect to the new location
 	// Otherwise, the JS fetch will follow the redirection and read a "login" page, embed it to the current page, which is not expected.
 	if httplib.IsGiteaFetchActionRequest(b.Req) {