[monitoring] Add inlineScrapeConfig support to tenant vmagent (#2200)

## Summary

- Adds `inlineScrapeConfig` support to the tenant `VMAgent` resource in
`packages/system/monitoring/templates/vm/vmagent.yaml`
- Adds commented usage example in both
`packages/system/monitoring/values.yaml` and
`packages/extra/monitoring/values.yaml`

## Problem

The tenant VMAgent resource does not support custom scrape
configurations. Using `additionalScrapeConfigs` (which references a
Kubernetes Secret) is not viable because tenant users have no access to
create or read Secrets — they can only manage resources under
`apps.cozystack.io`. Instead, `inlineScrapeConfig` accepts inline YAML
directly through Helm values, which is consistent with tenant
permissions.

Relates to #2194

## Usage

```yaml
vmagent:
  inlineScrapeConfig: |
    - job_name: "custom"
      static_configs:
        - targets: ["my-service:9090"]
```

## Test plan

- [ ] `helm template` monitoring with `inlineScrapeConfig` set — block
rendered
- [ ] `helm template` monitoring without it — no `inlineScrapeConfig` in
output
- [ ] Deploy and verify custom scrape targets are picked up by vmagent

```release-note
Add inlineScrapeConfig support to tenant vmagent
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Support for including an inline scrape configuration into VMAgent
monitoring when provided.

* **Documentation**
* Added a commented example showing how to supply an inline scrape job
and targets.
* Reordered remote-write URL entries in monitoring configuration for
clearer ordering.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/extra/monitoring/values.yaml

@@ -178,3 +178,7 @@ vmagent:
     urls:
       - http://vminsert-shortterm:8480/insert/0/prometheus
       - http://vminsert-longterm:8480/insert/0/prometheus
+  ## inlineScrapeConfig: |
+  ##   - job_name: "custom"
+  ##     static_configs:
+  ##       - targets: ["my-service:9090"]

packages/system/monitoring/templates/vm/vmagent.yaml

@@ -21,6 +21,10 @@ spec:
 
   scrapeInterval: 30s
   selectAllByDefault: false
+  {{- with .Values.vmagent.inlineScrapeConfig }}
+  inlineScrapeConfig: |
+    {{- . | nindent 4 }}
+  {{- end }}
   podScrapeNamespaceSelector:
     matchLabels:
       namespace.cozystack.io/monitoring: {{ .Release.Namespace }}

packages/system/monitoring/values.yaml

@@ -79,4 +79,8 @@ vmagent:
   remoteWrite:
     urls:
       - http://vminsert-shortterm:8480/insert/0/prometheus
-      - http://vminsert-longterm:8480/insert/0/prometheus
+      - http://vminsert-longterm:8480/insert/0/prometheus
+  ## inlineScrapeConfig: |
+  ##   - job_name: "custom"
+  ##     static_configs:
+  ##       - targets: ["my-service:9090"]