[PULP-659] Remove legacy django storages

[pedro-psb]

This PR does:

• Remove support for using DEFAULT_FILE_STORAGE (added in: [PULP-210] Update deprecated django storage config #6058)
• Apply plugin-template to remove both storage settings from CI settings.py (See: [PULP-659] Modify settings.py.j2 storages to work with older and newer branches plugin_template#975)

For Plugins

• When supporting 3.85, set test_storages_compat_layer: False in template_config.yml so it only renders the newer storage settings for every storage case (s3 and azure).
• The plugin pulpcore lowerbound must be >=3.70. If a pulpcore <3.70 is used, the CI installation can break (most likely on the lowerbound scenario), as it doest support the newer storage form.

[mdellweg]

Suggested change

	{%- if test_storages_compat_layer is not defined -%}
	{%- if s3_test | default(false) -%}{{ s3_settings(legacy=True) }}{%- endif -%}
	{%- if azure_test | default(false) -%}{{ azure_settings(legacy=True) }}{%- endif -%}
	{%- if gcp_test | default(false) -%}{{ gcp_settings(legacy=True) }}{%- endif -%}
	{%- else -%}
	{%- if test_storages_compat_layer is true -%}
	{%- if s3_test | default(false) -%}{{ s3_settings(legacy=False) }}{%- endif -%}
	{%- if azure_test | default(false) -%}{{ azure_settings(legacy=True) }}{%- endif -%}
	{%- if gcp_test | default(false) -%}{{ gcp_settings(legacy=True) }}{%- endif -%}
	{%- elif test_storages_compat_layer is false -%}
	{%- if s3_test | default(false) -%}{{ s3_settings(legacy=False) }}{%- endif -%}
	{%- if azure_test | default(false) -%}{{ azure_settings(legacy=False) }}{%- endif -%}
	{%- if gcp_test | default(false) -%}{{ gcp_settings(legacy=False) }}{%- endif -%}
	{%- endif -%}
	{%- endif -%}
	{%- if s3_test | default(false) -%}{{ s3_settings(legacy=test_storages_compat_layer is not defined) }}{%- endif -%}
	{%- if azure_test | default(false) -%}{{ azure_settings(legacy=test_storages_compat_layer | default(True)) }}{%- endif -%}
	{%- if gcp_test | default(false) -%}{{ gcp_settings(legacy=test_storages_compat_layer | default(True)) }}{%- endif -%}