Library schematic does not support path property

# 🐞 Bug report

### Command (mark with an `x`)

```
- [ ] new
- [ ] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc
- [X] schematics
```

### Is this a regression?

Not as far as I know

### Description

I tried to create a schematic that generates an application and adds a library to it. However, the library schematic does not accept a `path` as parameter and it then attempts to create the library in the folder that contains the application. Specifically, it tries to read the `angular.json` file from the folder containing the application folder (e.g. the folder where the schematic is run).

Note that I expected the `path` property to work, as it's included with most of the other Angular schematics, for example component, module and service.

## 🔬 Minimal Reproduction

A minimal reproduction may be found [in this repo](https://github.com/CobusKruger/AngularProjectMergeIssues).

It also addresses a problem I had when trying to work around this with `applyToSubtree`.

Here is the simplest description I could come up with.

Given this factory:

```typescript
export function createProject(_options: any): Rule {
return (_tree: Tree, _context: SchematicContext) => {
return chain([
externalSchematic('@schematics/angular', 'ng-new', optionsNew),
externalSchematic('@schematics/angular', 'library', optionsLib)
]);
};
}
```

If you execute the schematic in a folder named `/parent/folder` and the app generates in a new folder named app (`/parent/folder/app`), the library schematic searches for the `angular.json` in `/parent/folder` instead of `/parent/folder/app`.

## 🔥 Exception or Error
```
An error occured:
Error: Unable to locate a workspace file for workspace path.
at Object.readWorkspace (C:\dev\scratchpad\scaffolding-tests\node_modules\@angular-devkit\core\src\workspace\core.js:74:19)
at async Object.getWorkspace (C:\dev\scratchpad\scaffolding-tests\node_modules\@schematics\angular\utility\workspace.js:51:27)
at async C:\dev\scratchpad\scaffolding-tests\node_modules\@schematics\angular\library\index.js:153:27
```

## 🌍 Your Environment

     _                      _                 ____ _     ___

    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|

   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |

  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |

 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|

                |___/

    


Angular CLI: 8.3.1

Node: 12.12.0

OS: win32 x64

Angular: undefined

...

Package                      Version

------------------------------------------------------

@angular-devkit/architect    0.803.1 (cli-only)

@angular-devkit/core         8.3.17

@angular-devkit/schematics   8.3.17

@schematics/angular          8.3.1 (cli-only)

@schematics/update           0.803.1 (cli-only)

rxjs                         6.4.0

typescript                   3.5.3

## Similar issues
https://github.com/angular/angular-cli/issues/17598

Bắt đầu với repository tái hiện tối thiểu được liên kết trong issue và truy vết entry point của library schematic tại @schematics/angular/library/index.js, cùng với utility/workspace.js từ error stack. Xác nhận cách path được xử lý khi application được generate trong một subfolder. Được xem là hoàn tất khi library schematic chấp nhận path và định vị angular.json của application đã generate mà không gặp workspace error.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.