control_plane: database persistence for attachment_service (#6468)

## Problem

Spun off from https://github.com/neondatabase/neon/pull/6394 -- this PR
is just the persistence parts and the changes that enable it to work
nicely


## Summary of changes

- Revert #6444 and #6450
- In neon_local, start a vanilla postgres instance for the attachment
service to use.
- Adopt `diesel` crate for database access in attachment service. This
uses raw SQL migrations as the source of truth for the schema, so it's a
soft dependency: we can switch libraries pretty easily.
- Rewrite persistence.rs to use postgres (via diesel) instead of JSON.
- Preserve JSON read+write at startup and shutdown: this enables using
the JSON format in compatibility tests, so that we don't have to commit
to our DB schema yet.
- In neon_local, run database creation + migrations before starting
attachment service
- Run the initial reconciliation in Service::spawn in the background, so
that the pageserver + attachment service don't get stuck waiting for
each other to start, when restarting both together in a test.

pageserver/src/virtual_file.rs

@@ -403,7 +403,12 @@ impl VirtualFile {
         Ok(vfile)
     }
 
-    /// Async & [`VirtualFile`]-enabled version of [`::utils::crashsafe::overwrite`].
+    /// Writes a file to the specified `final_path` in a crash safe fasion
+    ///
+    /// The file is first written to the specified tmp_path, and in a second
+    /// step, the tmp path is renamed to the final path. As renames are
+    /// atomic, a crash during the write operation will never leave behind a
+    /// partially written file.
     pub async fn crashsafe_overwrite(
         final_path: &Utf8Path,
         tmp_path: &Utf8Path,