## Summary

Follow up to elastic#221568

This  PR allows specifying spaces param in project monitors.

Following use-cases have been supported

User will be able to supports

`spaces: ["defautl", "test"]
`

Proper API tests have been added to provide additional coverage for the
use-case.

### Validations

- [ ] The route to which project api is being called should always be
part of spaces if defined.
- [ ] Non existent space will throw error
- [ ] User must have permission to all specified spaces for CRUDS
- [ ] User can also specify * to create monitors in all spaces

### PR Testing
You can use following project monitors PR to test this PR
elastic/synthetics#1052

First create few project monitors before this branch and then switch and
specify multi spaces as part of the options and verify in UI that
editing , adding and deletion works as expected on push command.

(cherry picked from commit 39d87d0)