Only UnwindLLDB honored target.process.thread.max-backtrace-depth, so
UnwindWasm reported every frame the stub sent and a stack that recursed
without end was walked to its end.
Bound the frame count by the depth on every query rather than dropping
the frames that exceed it. A Wasm call stack arrives whole on the first
query, so a depth lowered after that has to still apply, which is when a
user reaches for it. The synthetic call frame addresses stay derived
from the whole stack, so the order of the frames does not depend on the
depth.
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