Add check for at least one route

[cprecioso]

Description

Fixes #2447

Checks that there is at least one route declared in the AppSpec.

I had to modify a handful of tests that worked with an empty AppSpec and now must have a route decl. Please suggest if there is a better way.

Select what type of change this PR introduces:

1. Just code/docs improvement (no functional change).
2. Bug fix (non-breaking change which fixes an issue).
3. New feature (non-breaking change which adds functionality).
4. Breaking change (fix or feature that would cause existing functionality to not work as expected).

Update Waspc ChangeLog and version if needed

If you did a bug fix, new feature, or breaking change, that affects waspc, make sure you satisfy the following:

1. I updated ChangeLog.md with description of the change this PR introduces.
2. I bumped waspc version in waspc.cabal to reflect changes I introduced, with regards to the version of the latest wasp release, if the bump was needed.

Update example apps if needed

If you did code changes and added a new feature or modified an existing feature, make sure you satisfy the following:

1. I updated waspc/examples/todoApp as needed (updated modified feature or added new feature) and manually checked it works correctly.
2. I updated waspc/headless-test/examples/todoApp and its e2e tests as needed (updated modified feature and its tests or added new feature and new tests for it).

[infomiho]

I think you did the right thing with updating unit tests the way you did 👍

[cprecioso]

@infomiho @Martinsos care to approve? ☺️

[infomiho]

LGTM