Allow underscores in integers and floats (#7759)

# Description

This PR makes changes that allow underscores in numbers.

Example:
```nu
# allows underscores to be placed arbitrarily to enhance readability.
let pi = 3.1415_9265_3589_793

# works with integers
let num = 1_000_000_000_000
let fav_color = 0x68_9d_6a
```

src/tests/test_parser.rs

@@ -18,6 +18,31 @@ fn alias_1() -> TestResult {
     run_test("def foo [$x] { $x + 10 }; alias f = foo; f 100", "110")
 }
 
+#[test]
+fn ints_with_underscores() -> TestResult {
+    run_test("1_0000_0000_0000 + 10", "1000000000010")
+}
+
+#[test]
+fn floats_with_underscores() -> TestResult {
+    run_test("3.1415_9265_3589_793 * 2", "6.283185307179586")
+}
+
+#[test]
+fn bin_ints_with_underscores() -> TestResult {
+    run_test("0b_10100_11101_10010", "21426")
+}
+
+#[test]
+fn oct_ints_with_underscores() -> TestResult {
+    run_test("0o2443_6442_7652_0044", "90422533333028")
+}
+
+#[test]
+fn hex_ints_with_underscores() -> TestResult {
+    run_test("0x68__9d__6a", "6856042")
+}
+
 #[test]
 fn alias_2() -> TestResult {
     run_test(