Improve SnippetsFilters telemetry collection

[bjee19]

Credit to @pleshakov , the telemetry collection of SnippetsFilters added in this PR has a few edge cases which lead to incorrect behavior. The issue comes up when parsing nginx directives and values. This is the current implementation of parsing Snippet values

func parseSnippetValueIntoDirectives(snippetValue string) []string {
	separatedDirectives := strings.Split(snippetValue, ";")
	directives := make([]string, 0, len(separatedDirectives))

	for _, directive := range separatedDirectives {
		// the strings.TrimSpace is needed in the case of multi-line NGINX Snippet values
		directive = strings.Split(strings.TrimSpace(directive), " ")[0]

		// splitting on the delimiting character can result in a directive being empty or a space/newline character,
		// so we check here to ensure it's not
		if directive != "" {
			directives = append(directives, directive)
		}
	}

	return directives
}

This current implementation is too lax on using the ; character as a separator for directives and leaves room for many edge cases to incorrectly get parsed.

Below are some examples:

Use of the map directive, which not only doesn't have the ; character at the end of the directive, but can have nested ; characters which are not directives.

input:

            {Namespace: "test", Name: "sf-1"}: {
                    Snippets: map[ngfAPI.NginxContext]string{
                            ngfAPI.NginxContextMain:               "worker_priority 0;",
                            ngfAPI.NginxContextHTTP:               "aio on; map $http_x $x {default 0; 'abc' 1;}",
                            ngfAPI.NginxContextHTTPServer:         "auth_delay 10s;",
                            ngfAPI.NginxContextHTTPServerLocation: "keepalive_time 10s;",
                    },

output:

          SnippetsFiltersDirectives: [
              "auth_delay-server",
              "aio-http",
              "keepalive_time-location",
              "worker_priority-main",
              "'abc'-http",
              "client_body_timeout-http",
              "map-http",
              "}-http",
              "allow-location",
              "worker_rlimit_core-main",
              "worker_rlimit_nofile-main",
              "ignore_invalid_headers-server",
          ],

Any example with ; included in the value.

proxy_set_header hello "myvalue;abc";

Comments in general, AND if ; is inside a comment

# this is a nasty; comment

[mpstefan]

Waiting to see what results we get in telemetry first. @kate-osborn May look at before then.