Remap borrowed inline iterator symbols in sema, restore strict codegen, and add distinct/borrow runtime tests

[Clemente90]

Motivation

• Ensure borrowed inline iterator bodies reference the borrowing iterator's symbols to avoid semantic mismatches and internal codegen errors when borrowing inline iterators.
• Keep runtime coverage for distinct/borrow behaviors (iterators, arrays, seq, Table, nested distinct conversions and borrowed methods) to prevent regressions.
• Restore stricter codegen/statement-location checks to avoid spurious internal errors during compilation of inline iterators.

Description

• Add replaceOwnedSyms and update semBorrow in compiler/semstmts.nim so that when an inline iterator is borrowed its body is copied and any symbols owned by the borrowed iterator are remapped to the borrowing iterator.
• Add runtime tests exercising borrowed iterators and nested distinct conversions in tests/distinct/ (tborrow_iterators.nim, tborrow_subclass_methods.nim, tdistinct_language_string.nim, tdistinct_nested.nim).
• Remove previously added relaxations in codegen/statement emission so the compiler keeps the original stricter checks (prevents "proc has no result symbol" and related internal errors for inline iterators).

Testing

• Ran bin/testament --print --nim:./bin/nim p tests/distinct and all tests in tests/distinct passed (43/43).
• Built and ran the iterator-specific test with ./koch temp c --hints:off tests/distinct/tborrow_iterators.nim and it completed successfully.
• Ran the bootstrap build ./koch boot -d:release --skipUserCfg --skipParentCfg --hints:off and it succeeded without error.

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Codex Task