[compute_ctl] Create check availability data during full configuration (#5084)

I've moved it to the API handler in the 589cf1ed2 to do not delay
compute start. Yet, we now skip full configuration and catalog updates
in the most hot path -- waking up suspended compute, and only do it at:

- first start
- start with applying new configuration
- start for availability check

so it doesn't really matter anymore.

The problem with creating the table and test record in the API handler
is that someone can fill up timeline till the logical limit. Then it's
suspended and availability check is scheduled, so it fails.

If table + test row are created at the very beginning, we reserve a 8 KB
page for future checks, which theoretically will last almost forever.
For example, my ~1y old branch still has 8 KB sized test table:
```sql
cloud_admin@postgres=# select pg_relation_size('health_check');
 pg_relation_size
------------------
             8192
(1 row)
```

---------

Co-authored-by: Anastasia Lubennikova <anastasia@neon.tech>

compute_tools/src/compute.rs

@@ -27,6 +27,7 @@ use utils::measured_stream::MeasuredReader;
 
 use remote_storage::{DownloadError, GenericRemoteStorage, RemotePath};
 
+use crate::checker::create_availability_check_data;
 use crate::pg_helpers::*;
 use crate::spec::*;
 use crate::sync_sk::{check_if_synced, ping_safekeeper};
@@ -696,6 +697,7 @@ impl ComputeNode {
         handle_role_deletions(spec, self.connstr.as_str(), &mut client)?;
         handle_grants(spec, self.connstr.as_str())?;
         handle_extensions(spec, &mut client)?;
+        create_availability_check_data(&mut client)?;
 
         // 'Close' connection
         drop(client);