[ET-VK] Deduplicate transition clone nodes in TagMemoryMetaPass

[SS-JIA]

Stack from ghstack (oldest at bottom):

• [ET-VK] Fused RMSNorm operator to fix fp16 overflow #18772
• -> [ET-VK] Deduplicate transition clone nodes in TagMemoryMetaPass #18771
• [ET-VK] Fix force_fp16 texture bias being silently rejected for CONTIGUOUS_ANY ops #18770

When the same tensor is consumed by multiple ops that need a different
storage representation, the pass previously inserted a separate clone
transition for each consumer. Now it caches transition clones keyed by
(source_node, target_storage_type, target_layout) and reuses existing
clones when the same transition is needed again.

For Qwen3 0.6B (8da4w fp16), the embedding output (BUFFER due to
vocab_size exceeding texture limits) feeds both rms_norm and add which
need TEXTURE. Previously 2 clones were inserted; now 1 clone is shared.

Authored by Claude.

Differential Revision: D100004700

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⏳ 1 Pending, 3 Unrelated Failures

As of commit 1710eed with merge base 4afd7f9 ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• Test Vulkan Backend / test-vulkan / test-backend-linux (vulkan, operators) / linux-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following jobs failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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