support core-1.7.0

[braingram]

Description

Support new "unstable" schemas (1.7.0) added in asdf-format/asdf-standard#479 by:

• adding new integer-1.2.0 and ndarray-1.2.0 tags to converters
• use "get_supported_core_schema_versions" from asdf-standard to dynamically set the supported versions (in part based on the presence of the ASDF_UNSTABLE_CORE_SCHEMAS environment variable)
• set ASDF_UNSTABLE_CORE_SCHEMAS in devdeps to test unstable version of schemas
• update several tests that started breaking with the unstable schemas. Most expected tags only in 1.6.0 (such as ndarray-1.1.0). These were updated in a way that should be compatible with future updates by dynamically inspecting the currently used tag or by forcing a core schema version (where the test was not designed to test the schema/extension but instead test the asdf implementation behavior).

The plan is for this PR will stay draft until after the asdf 5.0.0 release and then start testing and eventually update to 1.7.0 as part of a 5.x.x release (I'm not at the moment convinced that a change in default core schema should require a major version bump).

Closes: #1963

Requires asdf-format/asdf-standard#479 first to fix the devdeps (since the referenced Exception does not yet appear in asdf-standard main). Here's a run where the devdeps were run with the linked PR and passed.

Tasks

• run pre-commit on your machine
• run pytest on your machine
• Does this PR add new features and / or change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • update relevant docstrings and / or docs/ page
  • for any new features, add unit tests

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: bug fix
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[braingram]

I opened this for review but let's wait until asdf-format/asdf-standard#479 is merged and the CI here can be re-run to fix the devdeps.

[zacharyburnett]

approval for when this is ready