Explicitly defer node when attempting deferring an aliased modification in an imported macro function

[jasmith-hs]

Explicitly fail by creating a deferred node when attempting to defer modification of an alias outside of the context of an import.

This is a niche situation that we'd rather explicitly fail on than have incorrect logic. Handling this correctly is complex and likely not worth it.

Example:

{# 'eager/settings.jinja' #}
{% set settings = {} %}

{% macro load_settings() %}
{% do settings.put('foo', 'bar') %}
{% endmacro %}

{# 'main.jinja' #}
{% import 'eager/settings.jinja' as shared %}

{% if deferred %}
{{ shared.load_settings() }}
{% endif %}
{{ shared.settings }}

We don't know how that shared should be deferred so shared.settings ends up getting resolved as {}. This is what the output looks like before this PR:

{% if deferred %}
{% set __macro_load_settings_2043810590_temp_variable_0__ %}
{% set settings = {}  %}{% do settings.put('foo', 'bar') %}
{% endset %}{{ __macro_load_settings_2043810590_temp_variable_0__ }}
{% endif %}
{}

I tried actually supporting it, but since we can't reconstruct alias maps with macro functions inside of them outside of an import tag anyway, I decided to just short circuit the failure rather than adding a bunch of extra logic which ultimately flags the same failure condition. Here's that branch: ea4a7ac