Bug: constant-folded left shift `1 << (1 << 30)` OOMs the compiler

[anon-researchers-123]

Expected behavior

A shift count larger than the field bit-width should be rejected with a diagnostic
(there is an unused BitOverFlowInShift error variant for this), not turned into an
unbounded allocation.

The bug

A constant-folded left shift with a large shift count allocates a BigInt whose size is
the shift count in bits, with no upper bound, so the compiler hangs and eventually OOMs.

template T() {
    var v = 1 << (1 << 30);   // ~1**9-bit intermediate; hangs/OOMs
}
component main = T();

1 << (1 << 30) builds a ~1-billion-bit intermediate; 1 << (1 << 31) and up
OOM-kill the process on a typical CI runner.