fix: reduce cost of prebuild failure (#17697)

Relates to https://github.com/coder/coder/issues/17432

### Part 1:

Notes:
- `GetPresetsAtFailureLimit` SQL query is added, which is similar to
`GetPresetsBackoff`, they use same CTEs: `filtered_builds`,
`time_sorted_builds`, but they are still different.

- Query is executed on every loop iteration. We can consider marking
specific preset as permanently failed as an optimization to avoid
executing query on every loop iteration. But I decided don't do it for
now.

- By default `FailureHardLimit` is set to 3.

- `FailureHardLimit` is configurable. Setting it to zero - means that
hard limit is disabled.

### Part 2

Notes:
- `PrebuildFailureLimitReached` notification is added.
- Notification is sent to template admins.
- Notification is sent only the first time, when hard limit is reached.
But it will `log.Warn` on every loop iteration.
- I introduced this enum:
```sql
CREATE TYPE prebuild_status AS ENUM (
  'normal',           -- Prebuilds are working as expected; this is the default, healthy state.
  'hard_limited',     -- Prebuilds have failed repeatedly and hit the configured hard failure limit; won't be retried anymore.
  'validation_failed' -- Prebuilds failed due to a non-retryable validation error (e.g. template misconfiguration); won't be retried.
);
```
`validation_failed` not used in this PR, but I think it will be used in
next one, so I wanted to save us an extra migration.

- Notification looks like this:
<img width="472" alt="image"
src="https://github.com/user-attachments/assets/e10efea0-1790-4e7f-a65c-f94c40fced27"
/>

### Latest notification views:
<img width="463" alt="image"
src="https://github.com/user-attachments/assets/11310c58-68d1-4075-a497-f76d854633fe"
/>
<img width="725" alt="image"
src="https://github.com/user-attachments/assets/6bbfe21a-91ac-47c3-a9d1-21807bb0c53a"
/>

cli/testdata/server-config.yaml.golden

@@ -704,3 +704,7 @@ workspace_prebuilds:
   # backoff.
   # (default: 1h0m0s, type: duration)
   reconciliation_backoff_lookback_period: 1h0m0s
+  # Maximum number of consecutive failed prebuilds before a preset hits the hard
+  # limit; disabled when set to zero.
+  # (default: 3, type: int)
+  failure_hard_limit: 3