fix(@angular/cli): print ng update errors stack to log file

[alan-agius4]

When an error occurs during ng update we currently discard the stack trace which in some cases made it hard to identify the cause of the error.

Now, we print the stack trace to a log file similarly to unhandled exceptions.

Example of CMD output;

** Executing migrations of package '@angular/core' **

> Static flag migration.
  Removes the `static` flag from dynamic queries.
  As of Angular 9, the "static" flag defaults to false and is no longer required for your view and content queries.
  Read more about this here: https://v9.angular.io/guide/migration-dynamic-flag
× Migration failed: x
  See "C:\Users\alag\AppData\Local\Temp\ng-NgmC1G\angular-errors.log" for further details.

Example of log file contents:

[error] Error: x
    at UpdateCommand.executeSchematic (C:\git\angular-cli\test\node_modules\@angular\cli\commands\update-impl.js:98:19)
    at UpdateCommand.executePackageMigrations (C:\git\angular-cli\test\node_modules\@angular\cli\commands\update-impl.js:167:39)
    at UpdateCommand.executeMigrations (C:\git\angular-cli\test\node_modules\@angular\cli\commands\update-impl.js:161:21)
    at UpdateCommand.run (C:\git\angular-cli\test\node_modules\@angular\cli\commands\update-impl.js:394:38)
    at async UpdateCommand.validateAndRun (C:\git\angular-cli\test\node_modules\@angular\cli\models\command.js:134:28)
    at async Object.runCommand (C:\git\angular-cli\test\node_modules\@angular\cli\models\command-runner.js:201:24)
    at async default_1 (C:\git\angular-cli\test\node_modules\@angular\cli\lib\cli\index.js:62:31)

//cc @devversion

[devversion]

Awesome. Thanks @alan-agius4 for picking this up so fast! 🎉

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