[chore][postgresqlreceiver] do not report record if the total exec time is not changed (open-telemetry#39942)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

the current implementation would report queries not executed between the
last elapsed time. which is not ideal. it would flush the downstream.
this change will avoid the issue.

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#### Testing

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#### Documentation

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Author: cuichenli

.chloggen/fix-top-query-report-too-much.yaml

@@ -0,0 +1,28 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: postgresqlreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: fix too many top query got reported. top query should only report those queries were executed during the query interval
+
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39942]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/postgresqlreceiver/scraper.go

@@ -305,6 +305,9 @@ func (p *postgreSQLScraper) collectTopQuery(ctx context.Context, dbClient client
 				row[dbAttributePrefix+columnName] = finalValue
 			}
 		}
+		if row[dbAttributePrefix+totalExecTimeColumnName] == 0.0 {
+			continue
+		}
 		item := Item{
 			row:      row,
 			priority: row[dbAttributePrefix+totalExecTimeColumnName].(float64),