Further cleanup of Span::test_data usage + span fixes

[sholderbach]

Description

Inspired by #7592

For brevity use Value::test_{string,int,float,bool}

Includes fixes to commands that were abusing Span::test_data in their implementation. Now the call span is used where possible or the explicit Span::unknonw is used.

Command fixes

• Fix abuse of Span::test_data() in query_xml
• Fix abuse of Span::test_data() in term size
• Fix abuse of Span::test_data() in seq date
• Fix two abuses of Span::test_data in nu-cli
• Change Span::test_data to Span::unknown in keybindings listen
• Add proper call span to registry query
• Fix span use in nu_plugin_query
• Fix span assignment in select
• Use Span::unknown instead of test_data in more places

Other

• Use Value::test_int/test_float() consistently
• More test_string and test_bool
• Fix unused imports

User-Facing Changes

Some commands may now provide more helpful spans for downstream use in errors

[fdncred]

wow! lots more cleanup. good work!