Quantize lora linears

[lucylq]

Summary

LoraLinears contain:

1. base weight (nn.Linear)
2. lora_a (nn.Linear)
3. lora_b (nn.Linear)

(2) and (3) are caught by the filter, but (1) is not, as the weight and bias are pulled out of the nn.Linear and placed into nn.Parameters, and the linear is performed manually. This is for checkpoint compatibility - otherwise we'd have to map the weights for any lora model.

See:

executorch/examples/models/llama/lora.py

Lines 31 to 37 in b4d72f1

	linear = nn.Linear(in_dim, out_dim, bias=use_bias)
	weight = linear.weight
	bias = linear.bias if self.use_bias else None
	self.register_parameter("weight", nn.Parameter(weight))
	self.register_parameter(
	"bias", nn.Parameter(bias) if bias is not None else None
	)

This PR adds lora linears into the quantization filter.

Test plan

python -m extension.llm.export.export_llm \
    base.checkpoint="${DOWNLOADED_PATH}/consolidated.00.pth" \
    base.params="${DOWNLOADED_PATH}/params.json" \
    base.adapter_checkpoint="../et_docs_7_epoch/adapter_model.safetensors" \
    base.adapter_config="../et_docs_7_epoch/adapter_config.json" \
    base.tokenizer_path="../et_docs_7_epoch/" \
    model.use_kv_cache=true \
    model.use_sdpa_with_kv_cache=true \

Confirm output model size is ~1.7GB instead of 5.1GB.

(executorch) [lfq@devvm311.ldc0 /data/users/lfq/executorch (lfq.quantize-lora-linears)]$ ls -la *.pte
-rw-r--r-- 1 lfq users 5106135168 Nov 20 15:59 et_lora.pte
-rw-r--r-- 1 lfq users 1733835776 Nov 20 17:07 et_lora_fix.pte

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❌ 1 New Failure, 2 Unrelated Failures

As of commit c13f720 with merge base b4d72f1 ():

NEW FAILURE - The following job has failed:

• pull / unittest-editable / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_linear_model

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

• pull / unittest-editable / linux / linux-job (gh) (similar failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module

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

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

• pull / unittest / linux / linux-job (gh) (trunk failure)
  exir/backend/test/test_lowered_backend_module.py::TestBackendAPI::test_emit_nested_lowered_backend_module

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