Sometimes it's really convenient to run simple models thru the torchbench.py script rather than those from pytorch/benchmark. This PR add the ability to run any model from a specified path by overloading the --only argument.

This PR is split out from pytorch#88904

Here is the usage:

        Specify the path and class name of the model in format like:
        --only=path:<MODEL_FILE_PATH>,class:<CLASS_NAME>

        Due to the fact that dynamo changes current working directory,
        the path should be an absolute path.

        The class should have a method get_example_inputs to return the inputs
        for the model. An example looks like
        ```
        class LinearModel(nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = nn.Linear(10, 10)

            def forward(self, x):
                return self.linear(x)

            def get_example_inputs(self):
                return (torch.randn(2, 10),)
        ```

Test command:
```
# python benchmarks/dynamo/torchbench.py --performance --only=path:/pytorch/myscripts/model_collection.py,class:LinearModel --backend=eager
WARNING:common:torch.cuda.is_available() == False, using CPU
cpu  eval  LinearModel                        0.824x p=0.00
```

Content of model_collection.py
```
from torch import nn
import torch

class LinearModel(nn.Module):
    """
    AotAutogradStrategy.compile_fn ignore graph with at most 1 call nodes.
    Make sure this model calls 2 linear layers to avoid being skipped.
    """
    def __init__(self, nlayer=2):
        super().__init__()
        layers = []
        for _ in range(nlayer):
            layers.append(nn.Linear(10, 10))
        self.layers = nn.Sequential(*layers)

    def forward(self, x):
        return self.layers(x)

    def get_example_inputs(self):
        return (torch.randn(2, 10),)
```

Pull Request resolved: pytorch#89028
Approved by: https://github.com/jansel

Sometimes it's really convenient to run simple models thru the torchbench.py script rather than those from pytorch/benchmark. This PR add the ability to run any model from a specified path by overloading the --only argument.

This PR is split out from pytorch#88904

Here is the usage:

        Specify the path and class name of the model in format like:
        --only=path:<MODEL_FILE_PATH>,class:<CLASS_NAME>

        Due to the fact that dynamo changes current working directory,
        the path should be an absolute path.

        The class should have a method get_example_inputs to return the inputs
        for the model. An example looks like
        ```
        class LinearModel(nn.Module):
            def __init__(self):
                super().__init__()
                self.linear = nn.Linear(10, 10)

            def forward(self, x):
                return self.linear(x)

            def get_example_inputs(self):
                return (torch.randn(2, 10),)
        ```

Test command:
```
# python benchmarks/dynamo/torchbench.py --performance --only=path:/pytorch/myscripts/model_collection.py,class:LinearModel --backend=eager
WARNING:common:torch.cuda.is_available() == False, using CPU
cpu  eval  LinearModel                        0.824x p=0.00
```

Content of model_collection.py
```
from torch import nn
import torch

class LinearModel(nn.Module):
    """
    AotAutogradStrategy.compile_fn ignore graph with at most 1 call nodes.
    Make sure this model calls 2 linear layers to avoid being skipped.
    """
    def __init__(self, nlayer=2):
        super().__init__()
        layers = []
        for _ in range(nlayer):
            layers.append(nn.Linear(10, 10))
        self.layers = nn.Sequential(*layers)

    def forward(self, x):
        return self.layers(x)

    def get_example_inputs(self):
        return (torch.randn(2, 10),)
```

Pull Request resolved: pytorch#89028
Approved by: https://github.com/jansel