refactor: use serde for TenantConf deserialization Fixes: #5300 (#5310)

Remove handcrafted TenantConf deserialization code. Use
`serde_path_to_error` to include the field which failed parsing. Leaves
the duplicated TenantConf in pageserver and models, does not touch
PageserverConf handcrafted deserialization.

Error change:
- before change: "configure option `checkpoint_distance` cannot be
negative"
- after change: "`checkpoint_distance`: invalid value: integer `-1`,
expected u64"

Fixes: #5300
Cc: #3682

---------

Signed-off-by: Rahul Modpur <rmodpur2@gmail.com>
Co-authored-by: Shany Pozin <shany@neon.tech>
Co-authored-by: Joonas Koivunen <joonas@neon.tech>

libs/pageserver_api/src/models.rs

@@ -314,25 +314,7 @@ impl std::ops::Deref for TenantConfigRequest {
 
 impl TenantConfigRequest {
     pub fn new(tenant_id: TenantId) -> TenantConfigRequest {
-        let config = TenantConfig {
-            checkpoint_distance: None,
-            checkpoint_timeout: None,
-            compaction_target_size: None,
-            compaction_period: None,
-            compaction_threshold: None,
-            gc_horizon: None,
-            gc_period: None,
-            image_creation_threshold: None,
-            pitr_interval: None,
-            walreceiver_connect_timeout: None,
-            lagging_wal_timeout: None,
-            max_lsn_wal_lag: None,
-            trace_read_requests: None,
-            eviction_policy: None,
-            min_resident_size_override: None,
-            evictions_low_residence_duration_metric_threshold: None,
-            gc_feedback: None,
-        };
+        let config = TenantConfig::default();
         TenantConfigRequest { tenant_id, config }
     }
 }