delete timelines from s3 (#4384)

Delete data from s3 when timeline deletion is requested

## Summary of changes

UploadQueue is altered to support scheduling of delete operations in
stopped state. This looks weird, and I'm thinking whether there are
better options/refactorings for upload client to make it look better.

Probably can be part of https://github.com/neondatabase/neon/issues/4378

Deletion is implemented directly in existing endpoint because changes are not
that significant. If we want more safety we can separate those or create
feature flag for new behavior.

resolves [#4193](https://github.com/neondatabase/neon/issues/4193)

---------

Co-authored-by: Joonas Koivunen <joonas@neon.tech>

libs/pageserver_api/src/models.rs

@@ -152,7 +152,7 @@ pub enum ActivatingFrom {
 }
 
 /// A state of a timeline in pageserver's memory.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 pub enum TimelineState {
     /// The timeline is recognized by the pageserver but is not yet operational.
     /// In particular, the walreceiver connection loop is not running for this timeline.
@@ -165,7 +165,7 @@ pub enum TimelineState {
     /// It cannot transition back into any other state.
     Stopping,
     /// The timeline is broken and not operational (previous states: Loading or Active).
-    Broken,
+    Broken { reason: String, backtrace: String },
 }
 
 #[serde_as]