Set application_name for internal connections to computes

This will help when analyzing the origins of connections to a compute
like in [0].

[0]: neondatabase/cloud#14247

compute_tools/src/bin/compute_ctl.rs

@@ -735,7 +735,7 @@ fn cli() -> clap::Command {
             Arg::new("filecache-connstr")
                 .long("filecache-connstr")
                 .default_value(
-                    "host=localhost port=5432 dbname=postgres user=cloud_admin sslmode=disable",
+                    "host=localhost port=5432 dbname=postgres user=cloud_admin sslmode=disable application_name=vm-monitor",
                 )
                 .value_name("FILECACHE_CONNSTR"),
         )

vm-image-spec.yaml

@@ -18,7 +18,7 @@ commands:
   - name: postgres-exporter
     user: nobody
     sysvInitAction: respawn
-    shell: 'DATA_SOURCE_NAME="user=cloud_admin sslmode=disable dbname=postgres" /bin/postgres_exporter'
+    shell: 'DATA_SOURCE_NAME="user=cloud_admin sslmode=disable dbname=postgres application_name=postgres-exporter" /bin/postgres_exporter'
   - name: sql-exporter
     user: nobody
     sysvInitAction: respawn
@@ -93,7 +93,7 @@ files:
       target:
         # Data source name always has a URI schema that matches the driver name. In some cases (e.g. MySQL)
         # the schema gets dropped or replaced to match the driver expected DSN format.
-        data_source_name: 'postgresql://cloud_admin@127.0.0.1:5432/postgres?sslmode=disable'
+        data_source_name: 'postgresql://cloud_admin@127.0.0.1:5432/postgres?sslmode=disable&application_name=sql_exporter'
 
         # Collectors (referenced by name) to execute on the target.
         # Glob patterns are supported (see <https://pkg.go.dev/path/filepath#Match> for syntax).
@@ -128,7 +128,7 @@ files:
       target:
         # Data source name always has a URI schema that matches the driver name. In some cases (e.g. MySQL)
         # the schema gets dropped or replaced to match the driver expected DSN format.
-        data_source_name: 'postgresql://cloud_admin@127.0.0.1:5432/postgres?sslmode=disable'
+        data_source_name: 'postgresql://cloud_admin@127.0.0.1:5432/postgres?sslmode=disable&application_name=sql_exporter_autoscaling'
 
         # Collectors (referenced by name) to execute on the target.
         # Glob patterns are supported (see <https://pkg.go.dev/path/filepath#Match> for syntax).