Fix relative paths in commonjs decl emit w/property access (microsoft#40986)

```js
const x = require('./foo').y
```

was incorrectly using the unmangled require path as the temp name in
emit:

```
import ./foo_1 = require('./foo')
import x = ./foo_1.y
```

It now uses the imported identifier:

```
import x_1 = require('./foo')
import x = x_1.y
```

Discovered while fixing microsoft#37832

Author: sandersn

src/compiler/checker.ts

@@ -6788,16 +6788,16 @@ namespace ts {
                             if (isPropertyAccessExpression((node as VariableDeclaration).initializer!)) {
                                 // const x = require('y').z
                                 const initializer = (node as VariableDeclaration).initializer! as PropertyAccessExpression; // require('y').z
-                                const uniqueName = factory.createUniqueName((getExternalModuleRequireArgument(node) as StringLiteral).text); // _y
+                                const uniqueName = factory.createUniqueName(localName); // _x
                                 const specifier = getSpecifierForModuleSymbol(target.parent || target, context); // 'y'
-                                // import _y = require('y');
+                                // import _x = require('y');
                                 addResult(factory.createImportEqualsDeclaration(
                                     /*decorators*/ undefined,
                                     /*modifiers*/ undefined,
                                     uniqueName,
                                     factory.createExternalModuleReference(factory.createStringLiteral(specifier))
                                 ), ModifierFlags.None);
-                                // import x = _y.z
+                                // import x = _x.z
                                 addResult(factory.createImportEqualsDeclaration(
                                     /*decorators*/ undefined,
                                     /*modifiers*/ undefined,

tests/baselines/reference/jsDeclarationsCommonjsRelativePath.js

@@ -0,0 +1,22 @@
+//// [tests/cases/conformance/jsdoc/declarations/jsDeclarationsCommonjsRelativePath.ts] ////
+
+//// [thing.js]
+'use strict';
+class Thing {}
+module.exports = { Thing }
+
+//// [reexport.js]
+'use strict';
+const Thing = require('./thing').Thing
+module.exports = { Thing }
+
+
+
+
+//// [thing.d.ts]
+export class Thing {
+}
+//// [reexport.d.ts]
+import Thing_1 = require("./thing");
+import Thing = Thing_1.Thing;
+export { Thing };

tests/baselines/reference/jsDeclarationsCommonjsRelativePath.symbols

@@ -0,0 +1,26 @@
+=== tests/cases/conformance/jsdoc/declarations/reexport.js ===
+'use strict';
+const Thing = require('./thing').Thing
+>Thing : Symbol(Thing, Decl(reexport.js, 1, 5))
+>require('./thing').Thing : Symbol(Thing, Decl(thing.js, 2, 18))
+>require : Symbol(require)
+>'./thing' : Symbol("tests/cases/conformance/jsdoc/declarations/thing", Decl(thing.js, 0, 0))
+>Thing : Symbol(Thing, Decl(thing.js, 2, 18))
+
+module.exports = { Thing }
+>module.exports : Symbol("tests/cases/conformance/jsdoc/declarations/reexport", Decl(reexport.js, 0, 0))
+>module : Symbol(export=, Decl(reexport.js, 1, 38))
+>exports : Symbol(export=, Decl(reexport.js, 1, 38))
+>Thing : Symbol(Thing, Decl(reexport.js, 2, 18))
+
+=== tests/cases/conformance/jsdoc/declarations/thing.js ===
+'use strict';
+class Thing {}
+>Thing : Symbol(Thing, Decl(thing.js, 0, 13))
+
+module.exports = { Thing }
+>module.exports : Symbol("tests/cases/conformance/jsdoc/declarations/thing", Decl(thing.js, 0, 0))
+>module : Symbol(export=, Decl(thing.js, 1, 14))
+>exports : Symbol(export=, Decl(thing.js, 1, 14))
+>Thing : Symbol(Thing, Decl(thing.js, 2, 18))
+

tests/baselines/reference/jsDeclarationsCommonjsRelativePath.types

@@ -0,0 +1,35 @@
+=== tests/cases/conformance/jsdoc/declarations/reexport.js ===
+'use strict';
+>'use strict' : "use strict"
+
+const Thing = require('./thing').Thing
+>Thing : typeof Thing
+>require('./thing').Thing : typeof Thing
+>require('./thing') : { Thing: typeof Thing; }
+>require : any
+>'./thing' : "./thing"
+>Thing : typeof Thing
+
+module.exports = { Thing }
+>module.exports = { Thing } : { Thing: typeof Thing; }
+>module.exports : { Thing: typeof Thing; }
+>module : { "\"tests/cases/conformance/jsdoc/declarations/reexport\"": { Thing: typeof Thing; }; }
+>exports : { Thing: typeof Thing; }
+>{ Thing } : { Thing: typeof Thing; }
+>Thing : typeof Thing
+
+=== tests/cases/conformance/jsdoc/declarations/thing.js ===
+'use strict';
+>'use strict' : "use strict"
+
+class Thing {}
+>Thing : Thing
+
+module.exports = { Thing }
+>module.exports = { Thing } : { Thing: typeof Thing; }
+>module.exports : { Thing: typeof Thing; }
+>module : { "\"tests/cases/conformance/jsdoc/declarations/thing\"": { Thing: typeof Thing; }; }
+>exports : { Thing: typeof Thing; }
+>{ Thing } : { Thing: typeof Thing; }
+>Thing : typeof Thing
+

tests/baselines/reference/jsDeclarationsTypeReferences.js

@@ -28,5 +28,5 @@ module.exports = {
 //// [index.d.ts]
 /// <reference types="node" />
 export const thing: Something;
-import fs_1 = require("fs");
-import Something = fs_1.Something;
+import Something_1 = require("fs");
+import Something = Something_1.Something;

tests/baselines/reference/jsDeclarationsTypeReferences3.js

@@ -30,5 +30,5 @@ export namespace A {
         const thing: Something;
     }
 }
-import fs_1 = require("fs");
-import Something = fs_1.Something;
+import Something_1 = require("fs");
+import Something = Something_1.Something;

tests/cases/conformance/jsdoc/declarations/jsDeclarationsCommonjsRelativePath.ts

@@ -0,0 +1,13 @@
+// @checkJs: true
+// @declaration: true
+// @emitDeclarationOnly: true
+// @module: commonjs
+// @Filename: thing.js
+'use strict';
+class Thing {}
+module.exports = { Thing }
+
+// @Filename: reexport.js
+'use strict';
+const Thing = require('./thing').Thing
+module.exports = { Thing }