feat(error): name the callee/target in attempt to call/index errors

[davydog187]

Summary

• Annotates :call, :get_field, :set_field, :get_table, :set_table, and :self instructions with a compile-time name_hint derived from the AST ({:global, name} / {:local, name} / {:upvalue, name} / {:field, name} / {:method, name}).
• Executor formats the hint into the runtime error message, mirroring PUC-Lua.
• Fixes :set_field / :set_table to raise :index_non_table instead of MatchError when the target isn't a table.

Before

> Lua.eval!("return foo()")
attempt to call a nil value

> Lua.eval!("foo.bar()")
attempt to index a nil value

After

> Lua.eval!("return foo()")
attempt to call a nil value (global 'foo')

> Lua.eval!("foo.bar()")
attempt to index a nil value (global 'foo')

> Lua.eval!("local t = {}; t.bar()")
attempt to call a nil value (field 'bar')

> Lua.eval!("local t = {}; t:baz()")
attempt to call a nil value (method 'baz')

> Lua.eval!("local n = 5; return n.x")
attempt to index a number value (local 'n')

PUC-Lua recovers the same names via debug info threaded through bytecode; doing it at compile time is simpler here because the AST is still in scope when we emit the instruction.

Test plan

• mix test test/lua/error_messages_test.exs — 36 tests including 10 new cases covering global/local/upvalue/field/method calls, set-side index, non-function/non-table targets, and the anonymous-callee (no-hint) case.
• mix test — full suite (1778 tests, 30 skipped) passes.
• Manual iex -S mix smoke test for each error path.

[davydog187]

For the case where we're invoking functions and methods, it would be nice it if provided this information, i.e. I want to see that it was the t.bar() that failed (the 't' symbol is not mentioned in the current). Its definitely important to note which is nil as well (bar is nil, not t)