Align GUC initializations with boot values

As of upstream a73952b795 (16devel), custom GUCs have their initialized
values checked against the configured boot value. If they differ, an
assertion is tripped. So I've gone through the list and aligned the two
sides, adding defaults where they did not previously exist for
consistency.

To allow for dynamic boot values, the new assertion logic allows the
initialized value to be zero, in which case any boot value will be
accepted. ts_guc_max_open_chunks_per_insert relies on the value of
work_mem, so I've removed its (explicit) initializer entirely.

src/guc.c

@@ -80,8 +80,8 @@ bool ts_guc_enable_parameterized_data_node_scan = true;
 bool ts_guc_enable_async_append = true;
 TSDLLEXPORT bool ts_guc_enable_compression_indexscan = true;
 TSDLLEXPORT bool ts_guc_enable_skip_scan = true;
-int ts_guc_max_open_chunks_per_insert = 10;
-int ts_guc_max_cached_chunks_per_hypertable = 10;
+int ts_guc_max_open_chunks_per_insert; /* default is computed at runtime */
+int ts_guc_max_cached_chunks_per_hypertable = 100;
 #ifdef USE_TELEMETRY
 TelemetryLevel ts_guc_telemetry_level = TELEMETRY_DEFAULT;
 char *ts_telemetry_cloud = NULL;
@@ -90,10 +90,10 @@ char *ts_telemetry_cloud = NULL;
 TSDLLEXPORT char *ts_guc_license = TS_LICENSE_DEFAULT;
 char *ts_last_tune_time = NULL;
 char *ts_last_tune_version = NULL;
-TSDLLEXPORT bool ts_guc_enable_2pc;
+TSDLLEXPORT bool ts_guc_enable_2pc = true;
 TSDLLEXPORT int ts_guc_max_insert_batch_size = 1000;
-TSDLLEXPORT bool ts_guc_enable_connection_binary_data;
-TSDLLEXPORT DistCopyTransferFormat ts_guc_dist_copy_transfer_format;
+TSDLLEXPORT bool ts_guc_enable_connection_binary_data = true;
+TSDLLEXPORT DistCopyTransferFormat ts_guc_dist_copy_transfer_format = DCTF_Auto;
 TSDLLEXPORT bool ts_guc_enable_client_ddl_on_data_nodes = false;
 TSDLLEXPORT char *ts_guc_ssl_dir = NULL;
 TSDLLEXPORT char *ts_guc_passfile = NULL;
@@ -104,7 +104,7 @@ TSDLLEXPORT int ts_guc_hypertable_replication_factor_default = 1;
 
 #ifdef TS_DEBUG
 bool ts_shutdown_bgw = false;
-char *ts_current_timestamp_mock = "";
+char *ts_current_timestamp_mock = NULL;
 #endif
 
 /*