Alerting: add template funcs (#38404)

* Alerting: (wip) add template funcs

* Alerting: (wip) numeric template functions

* Alerting: (wip) template functions

* Test for the "args" function

* Alerting: (wip) Documentation for template functions

* Alerting: template functions - refactor

* code review changes

* disable linter error

* Use Prometheus implementation of TemplateExpander

* Update docs/sources/alerting/unified-alerting/alerting-rules/create-grafana-managed-rule.md

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/infra/process/root_check.go

@@ -1,3 +1,4 @@
+//go:build !windows
 // +build !windows
 
 package process

pkg/infra/process/root_check_windows.go

@@ -1,3 +1,4 @@
+//go:build windows
 // +build windows
 
 package process