Apply fieldalignment to collectdreceiver (#37321)

This change applies to structs in the hot path of the collectd receiver
and therefore impacting performance.

Author: atoulme

.chloggen/fieldalignment_collectdreceiver.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: collectdreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: apply fieldalignment to collectd records to reduce memory allocation
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [37321]
+
+# (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: []

receiver/collectdreceiver/collectd.go

@@ -17,25 +17,25 @@ import (
 )
 
 type collectDRecord struct {
-	Dsnames        []*string      `json:"dsnames"`
-	Dstypes        []*string      `json:"dstypes"`
+	Time           *float64       `json:"time"`
 	Host           *string        `json:"host"`
 	Interval       *float64       `json:"interval"`
 	Plugin         *string        `json:"plugin"`
 	PluginInstance *string        `json:"plugin_instance"`
-	Time           *float64       `json:"time"`
 	TypeS          *string        `json:"type"`
 	TypeInstance   *string        `json:"type_instance"`
-	Values         []*json.Number `json:"values"`
 	Message        *string        `json:"message"`
 	Meta           map[string]any `json:"meta"`
 	Severity       *string        `json:"severity"`
+	Dstypes        []*string      `json:"dstypes"`
+	Dsnames        []*string      `json:"dsnames"`
+	Values         []*json.Number `json:"values"`
 }
 
 type createMetricInfo struct {
-	Name   string
 	DsType *string
 	Val    *json.Number
+	Name   string
 }
 
 func (cdr *collectDRecord) isEvent() bool {