feat: replace eval_global_as_array_length with type/interpreter evaluation

[michaeljklein]

Description

Problem*

Resolves #6238

Summary*

Current plan:

• Resolve globals to:
  1. Type::InfixExpr / Type::Constant if possible
  • Where nested globals can be appx. Type::Global(GlobalId)
  3. comptime globals otherwise (to allow using the existing interpreter)
  • Require such globals to be explicitly comptime
• Use existing type-checking and interpreting code paths instead of eval_global_as_array_length

Additional Context

• numeric_generic_field_larger_than_u32: Using large Field's in numeric generics fails with "array length too large" #6125
• numeric_generic_field_arithmetic_larger_than_u32: Field computed to be larger than u32::MAX with arithmetic generics panics #6126

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[TomAFrench]

Discussed in 1:1 that we're going to require globals to have their type declared explicitly which also fixes the issues in this PR.