Deprecate the nu_scripts version of stdlib-candidate (#1042)

Deprecates the existing `stdlib-candidate` directories in `nu_scripts`
since `std-rfc` has now transitioned to the main repo. Updates readme
and renamed directories.

stdlib-candidate-archive/stdlib-candidate-older/tests/math.nu

@@ -0,0 +1,29 @@
+use std assert
+use ../std-rfc/math
+
+#[test]
+export def "test significant-digits-decimals" [] {
+    assert equal (0.0000012346789 | math significant-digits 2) 0.0000012
+    assert equal (11 / 3 | math significant-digits 6) 3.66666
+    assert not equal (0.0000012346789 | math significant-digits 2) 0.00000123
+    assert equal (1.999999 | math significant-digits 1) 1.0
+}
+
+#[test]
+export def "test significant-digits-duration" [] {
+    assert equal (2min / 7 | math significant-digits 3) 17100000000ns
+    assert equal (1sec | math significant-digits 3) 1000000000ns
+}
+
+#[test]
+export def "test significant-digits-ints" [] {
+    assert equal (123456 | math significant-digits 2) 120000
+}
+
+export def "test significant-digits-0" [] {
+    assert equal (0 | math significant-digits 2) 0
+}
+
+export def "test significant-digits-negative" [] {
+    assert equal (-1.23456789 | math significant-digits 5) (-1.2346)
+}