test: vaidate Bats minimum required version in tests

[hyperupcall]

Summary

According to Bats, the just-merged usage of setup_suite.bash was added in Bats 1.7. Conveniently, a bats_require_minimum_version was also added to assert the minimum Bats version.

This uses that, partially addressing #1435

The assertion must be in test_helpers.bash, because versions under 1.7 won't even automatically source setup_suite.bash, making the assertion useless

[jthegedus]

I did read about this, and in relation to #1435 have been thinking if we should validate min versions not just in docs but as assertions in the code itself.

This specific update would only be useful for those who aren't using asdf to manage their deps in this codebase, as our CI uses the same version of Bats as defined in .tool-versions.

[jthegedus]

In general, I approve this idea, though it is only useful if:

• people are aware we are using this Bats feature (bats_require_minimum_version) when expanding our Bats API usage in tests and know to update this min version
• people are not using asdf to manage their development tools for this repo as the version defined in .tool-versions is above this minimum

Given this is low impact I will approve and merge as a step towards #1435