Add es2018.intl ref to es2020.intl (microsoft#49152)

* Add es2018.intl ref to es2020.intl

es2020.intl refers to NumberFormatPartTypes declared in es2018.intl
as of microsoft#46508.

I'm not sure how to test this; it repros on Definitely Typed in
types/ndarray, but when I copy the same files into a compiler test it
passes without a problem.

* Add a test that shows the change works

It doesn't actually show that the original bug has been fixed,
though.

Author: sandersn

src/lib/es2020.intl.d.ts

@@ -1,3 +1,4 @@
+/// <reference lib="es2018.intl" />
 declare namespace Intl {
 
     /**

tests/baselines/reference/es2020IntlAPIs.errors.txt

@@ -53,22 +53,22 @@ tests/cases/conformance/es2020/es2020IntlAPIs.ts(50,29): error TS2345: Argument
     new Intl.Locale(); // should error
     ~~~~~~~~~~~~~~~~~
 !!! error TS2554: Expected 1-2 arguments, but got 0.
-!!! related TS6210 /.ts/lib.es2020.intl.d.ts:335:14: An argument for 'tag' was not provided.
+!!! related TS6210 /.ts/lib.es2020.intl.d.ts:336:14: An argument for 'tag' was not provided.
     new Intl.Locale(new Intl.Locale('en-US'));
 
     new Intl.DisplayNames(); // TypeError: invalid_argument
     ~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2554: Expected 2 arguments, but got 0.
-!!! related TS6210 /.ts/lib.es2020.intl.d.ts:414:13: An argument for 'locales' was not provided.
+!!! related TS6210 /.ts/lib.es2020.intl.d.ts:415:13: An argument for 'locales' was not provided.
     new Intl.DisplayNames('en'); // TypeError: invalid_argument
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2554: Expected 2 arguments, but got 1.
-!!! related TS6210 /.ts/lib.es2020.intl.d.ts:414:39: An argument for 'options' was not provided.
+!!! related TS6210 /.ts/lib.es2020.intl.d.ts:415:39: An argument for 'options' was not provided.
     new Intl.DisplayNames('en', {}); // TypeError: invalid_argument
                                 ~~
 !!! error TS2345: Argument of type '{}' is not assignable to parameter of type 'DisplayNamesOptions'.
 !!! error TS2345:   Property 'type' is missing in type '{}' but required in type 'DisplayNamesOptions'.
-!!! related TS2728 /.ts/lib.es2020.intl.d.ts:357:9: 'type' is declared here.
+!!! related TS2728 /.ts/lib.es2020.intl.d.ts:358:9: 'type' is declared here.
     console.log((new Intl.DisplayNames(undefined, {type: 'language'})).of('en-GB')); // "British English"
 
     const localesArg = ["es-ES", new Intl.Locale("en-US")];

tests/baselines/reference/esnext.bigintIncludesNumberFormatPartTypes.js

@@ -0,0 +1,8 @@
+//// [esnext.bigintIncludesNumberFormatPartTypes.ts]
+/// <reference lib="esnext.bigint" />
+var t: Intl.NumberFormatPartTypes
+
+
+//// [esnext.bigintIncludesNumberFormatPartTypes.js]
+/// <reference lib="esnext.bigint" />
+var t;

tests/baselines/reference/esnext.bigintIncludesNumberFormatPartTypes.symbols

@@ -0,0 +1,7 @@
+=== tests/cases/compiler/esnext.bigintIncludesNumberFormatPartTypes.ts ===
+/// <reference lib="esnext.bigint" />
+var t: Intl.NumberFormatPartTypes
+>t : Symbol(t, Decl(esnext.bigintIncludesNumberFormatPartTypes.ts, 1, 3))
+>Intl : Symbol(Intl, Decl(lib.es5.d.ts, --, --), Decl(lib.es2018.intl.d.ts, --, --), Decl(lib.es2020.bigint.d.ts, --, --), Decl(lib.es2020.intl.d.ts, --, --))
+>NumberFormatPartTypes : Symbol(Intl.NumberFormatPartTypes, Decl(lib.es2018.intl.d.ts, --, --))
+

tests/baselines/reference/esnext.bigintIncludesNumberFormatPartTypes.types

@@ -0,0 +1,6 @@
+=== tests/cases/compiler/esnext.bigintIncludesNumberFormatPartTypes.ts ===
+/// <reference lib="esnext.bigint" />
+var t: Intl.NumberFormatPartTypes
+>t : Intl.NumberFormatPartTypes
+>Intl : any
+

tests/cases/compiler/esnext.bigintIncludesNumberFormatPartTypes.ts

@@ -0,0 +1,3 @@
+// @lib: es6
+/// <reference lib="esnext.bigint" />
+var t: Intl.NumberFormatPartTypes