[receiver/hostmetrics] Allow process scraper under FreeBSD (#39622)

#### Description
Allow the `process` scraper to be used under FreeBSD for the
`hostmetrics` receiver, doing the same handling as done for MacOS.

#### Documentation
Update the available scrapers table:
* added FreeBSD as supported OS for the `process` scraper after the code
updates in the PR
* added FreeBSD / OpenBSD as supported OSs for the `processes` scraper.
Fixed documentation error, since this scraper could already be used in
these two OSs

Author: nozomi-gedimitr

.chloggen/hostmetricsreceiver_process_scraper_freebsd.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: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Possible to enable the process scraper under FreeBSD in the hostmetrics receiver.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [39622]
+
+# (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/hostmetricsreceiver/README.md

@@ -47,8 +47,8 @@ The available scrapers are:
 | [memory]     | All                          | Memory utilization metrics                             |
 | [network]    | All                          | Network interface I/O metrics & TCP connection metrics |
 | [paging]     | All                          | Paging/Swap space utilization and I/O metrics          |
-| [processes]  | Linux, Mac                   | Process count metrics                                  |
-| [process]    | Linux, Windows, Mac          | Per process CPU, Memory, and Disk I/O metrics          |
+| [processes]  | Linux, Mac, FreeBSD, OpenBSD | Process count metrics                                  |
+| [process]    | Linux, Windows, Mac, FreeBSD | Per process CPU, Memory, and Disk I/O metrics          |
 | [system]     | Linux, Windows, Mac          | Miscellaneous system metrics                           |
 
 [cpu]: ./internal/scraper/cpuscraper/documentation.md

receiver/hostmetricsreceiver/internal/scraper/processscraper/factory.go

@@ -44,8 +44,8 @@ func createMetricsScraper(
 	settings scraper.Settings,
 	cfg component.Config,
 ) (scraper.Metrics, error) {
-	if runtime.GOOS != "linux" && runtime.GOOS != "windows" && runtime.GOOS != "darwin" {
-		return nil, errors.New("process scraper only available on Linux, Windows, or macOS")
+	if runtime.GOOS != "linux" && runtime.GOOS != "windows" && runtime.GOOS != "darwin" && runtime.GOOS != "freebsd" {
+		return nil, errors.New("process scraper only available on Linux, Windows, macOS, or FreeBSD")
 	}
 
 	s, err := newProcessScraper(settings, cfg.(*Config))

receiver/hostmetricsreceiver/internal/scraper/processscraper/factory_test.go

@@ -26,7 +26,7 @@ func TestCreateResourceMetricsScraper(t *testing.T) {
 
 	scraper, err := factory.CreateMetrics(context.Background(), scrapertest.NewNopSettings(metadata.Type), cfg)
 
-	if runtime.GOOS == "linux" || runtime.GOOS == "windows" || runtime.GOOS == "darwin" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "freebsd" {
 		assert.NoError(t, err)
 		assert.NotNil(t, scraper)
 	} else {

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_darwin.go renamed to receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_bsds.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-//go:build darwin
+//go:build darwin || freebsd
 
 package processscraper // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper"
 

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_others.go

@@ -1,7 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
-//go:build !linux && !windows && !darwin
+//go:build !linux && !windows && !darwin && !freebsd
 
 package processscraper // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper"