PG16: Align GUC variables initial value with boot values

Any value hardcoded to a GUC variable will be overwritten by the
boot_value when the GUC mechanism starts up. PG16 makes this more clear
by checking that if a hardcoded value exists, it is same as the
boot_value. The server asserts in debug builds if values are not equal.

Commit 0963609 already fixes most of our code to align the hardcoded
and boot_values for various GUC variables. This patch updates only the
ts_guc_max_cached_chunks_per_hypertable initialisation which
had an initial value different from the boot_value.

postgres/postgres@a73952b79

src/guc.c

@@ -85,8 +85,10 @@ bool ts_guc_enable_async_append = true;
 TSDLLEXPORT bool ts_guc_enable_compression_indexscan = true;
 TSDLLEXPORT bool ts_guc_enable_bulk_decompression = true;
 TSDLLEXPORT bool ts_guc_enable_skip_scan = true;
-int ts_guc_max_open_chunks_per_insert; /* default is computed at runtime */
-int ts_guc_max_cached_chunks_per_hypertable = 100;
+/* default value of ts_guc_max_open_chunks_per_insert and ts_guc_max_cached_chunks_per_hypertable
+ * will be set as their respective boot-value when the GUC mechanism starts up */
+int ts_guc_max_open_chunks_per_insert;
+int ts_guc_max_cached_chunks_per_hypertable;
 #ifdef USE_TELEMETRY
 TelemetryLevel ts_guc_telemetry_level = TELEMETRY_DEFAULT;
 char *ts_telemetry_cloud = NULL;