v2: Allow overriding Alloy modules configmaps name prefix

[splichy]

fix for #994

Using .Values.global was the simplest way to pass fullnameOverride to both umbrella & child charts.

With:

clusterMetrics:
  enabled: true
  kepler:
    fullnameOverride: kepler
  opencost:
    fullnameOverride: opencost
podLogs:
  enabled: true
nodeLogs:
  enabled: true
clusterEvents:
  enabled: true

alloy-metrics:
  fullnameOverride: alloy-metrics
  enabled: true
alloy-logs:
  fullnameOverride: alloy-logs
  enabled: true
alloy-singleton:
  fullnameOverride: alloy-singleton
  enabled: true

configmap name will be like: very-long-release-name-alloy-module-kubernetes

adding:

global:
fullnameOverride: k8s-monitoring

will render configmap name as k8s-monitoring-alloy-module-kubernetes:

---
# Source: k8s-monitoring/charts/k8s-monitoring/templates/alloy-modules-configmaps.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: k8s-monitoring-alloy-module-kubernetes
// ...REMOVED FOR CLARITY

including its reference in resulting configmap data:

---
# Source: k8s-monitoring/charts/k8s-monitoring/templates/alloy-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: alloy-metrics
  namespace: monitoring
data:
  config.alloy: |-
    // Destination: prometheus (prometheus)
// ...REMOVED FOR CLARITY
    // Feature: Cluster Metrics
    declare "cluster_metrics" {
      argument "metrics_destinations" {
        comment = "Must be a list of metric destinations where collected metrics should be forwarded to"
      }
      
      remote.kubernetes.configmap "kubernetes" {
        name = "k8s-monitoring-alloy-module-kubernetes"
        namespace = "monitoring"
      }
// ...REMOVED FOR CLARITY

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