Preallocate a map of the right size in pcommon Map.AsRaw() (#12406)

#### Description
We are seeing pcommon/Map.AsRaw() show up in the memory profiles.

This PR ensure we pre-allocate a map[string]any of the expected size,
instead of just an empty map.

---------

Co-authored-by: Bogdan Drutu <[email protected]>

Author: kamstrup

.chloggen/pcommon-map-asraw-prealloc.yaml

@@ -0,0 +1,25 @@
+# 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. otlpreceiver)
+component: pcommon.Map
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: preallocate go map in Map.AsRaw()
+
+# One or more tracking issues or pull requests related to the change
+issues: [12406]
+
+# (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:
+
+# 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: [api]

pdata/pcommon/map.go

@@ -263,7 +263,7 @@ func (m Map) CopyTo(dest Map) {
 
 // AsRaw returns a standard go map representation of this Map.
 func (m Map) AsRaw() map[string]any {
-	rawMap := make(map[string]any)
+	rawMap := make(map[string]any, m.Len())
 	m.Range(func(k string, v Value) bool {
 		rawMap[k] = v.AsRaw()
 		return true