fix lexeer issue, it's value to have numbers inside the field (just n…

…ot at the start)

Also simplified logic

pkg/logql/log/jsonexpr/lexer.go

@@ -68,7 +68,7 @@ func (sc *Scanner) lex(lval *JSONExprSymType) int {
 			return RSB
 		case r == '.':
 			return DOT
-		case isIdentifier(r):
+		case isStartIdentifier(r):
 			sc.unread()
 			lval.field = sc.scanField()
 			return FIELD
@@ -83,21 +83,20 @@ func (sc *Scanner) lex(lval *JSONExprSymType) int {
 	}
 }
 
-func isIdentifier(r rune) bool {
+func isStartIdentifier(r rune) bool {
 	return (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || r == '_'
 }
 
+func isIdentifier(r rune) bool {
+	return (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '_'
+}
+
 func (sc *Scanner) scanField() string {
 	var str []rune
 
 	for {
 		r := sc.read()
-		if !isIdentifier(r) {
-			sc.unread()
-			break
-		}
-
-		if r == '.' || isEndOfInput(r) {
+		if !isIdentifier(r) || isEndOfInput(r) {
 			sc.unread()
 			break
 		}