change: fully deprecated the acceptance of value field in VirtualTables

[eliot1480]

Which issue does this PR close?

#23608

• Closes Remove usages of deprecated VirtualTable.values field #23608

Rationale for this change

This PR is the final step in fully deprecating the VirtualTables.values, as we now only allow the consumption of expressions instead of the value field as well.

What changes are included in this PR?

These changes remove the deprecated VirtualTable.values consumer path, including the old literal-row conversion helper and the broad deprecation allowance around from_read_rel. The consumer now handles empty virtual tables, one-row empty relations, and normal virtual table rows using VirtualTable.expressions only.

Are these changes tested?

Yes.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.12500% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.18%. Comparing base (f171587) to head (a03ba1f).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ubstrait/src/logical_plan/consumer/rel/read_rel.rs	78.12%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #24346   +/-   ##
=======================================
  Coverage   81.17%   81.18%           
=======================================
  Files        1109     1109           
  Lines      388033   387995   -38     
  Branches   388033   387995   -38     
=======================================
- Hits       314985   314975   -10     
+ Misses      54509    54478   -31     
- Partials    18539    18542    +3     

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