Ability to use sprig functions in analyzer templates

[sgalsaleh]

Description, Motivation and Context

This change adds support for using Sprig template functions in analyzer templates. The Sprig library provides a comprehensive set of template functions that are commonly used in Go templating, which will give users more flexibility and power when writing analyzer templates.

Checklist

• New and existing tests pass locally with introduced changes.
• Tests for the changes have been added (for bug fixes / features)
• The commit message(s) are informative and highlight any breaking changes
• Any documentation required has been added/updated.

Does this PR introduce a breaking change?

• Yes
• No

[jtuchscherer]

I am always going to advocate for adding a unit :-)
Something like this in util_test.go:

		{
			name:    "template with sprig function works",
			tpl:     "{{ \"hello \" | upper }}{{ .Name }}",
			data:    map[string]string{"Name": "World"},
			want:    "HELLO World",
			wantErr: false,
		},
		{
			name:    "template with undefined sprig function errors",
			tpl:     "{{ \"hello \" | upp }}{{ .Name }}",
			data:    map[string]string{"Name": "World"},
			want:    "",
			wantErr: true,
		},

(I tried this locally)