Update pydantic support to v2

[rahul-tuli]

This PR updates sparseml pydantic support to v2

Steps:

• use pydantic's official bump pydantic tool for pre-liminary migration
• update setup.py
• fix model configs and typing
• update recipe serialization, also fixes a bug with original serialization

Test methodology:

• make test targets=torch passes locally
• sanity check with a dummy recipe containing multiple stages and multiple groups within each stage
• test script attached with description

Sanity Script:

# local/feature/main.py

from sparseml.core import Recipe
import pprint as pp

import yaml

pp = pp.PrettyPrinter(indent=4)

recipe = """

first_oneshot_stage:
    pruning_modifiers:
        ConstantPruningModifier:
            start_epoch: 0
            end_epoch: 5
            targets: __ALL_PRUNABLE__

        MagnitudePruningModifier:
            start_epoch: 5
            end_epoch: 10
            init_sparsity: 0.1
            final_sparsity: 0.5
            targets: __ALL_PRUNABLE__

    quantization_modifiers:
        QuantizationModifier:
            start_epoch: 10
            end_epoch: 15
            bits: 8
            targets: __ALL_PRUNABLE__

second_oneshot_stage:
    pruning_modifiers:
        ConstantPruningModifier:
            start_epoch: 15
            end_epoch: 20
            targets: __ALL_PRUNABLE__

        MagnitudePruningModifier:
            start_epoch: 20
            end_epoch: 25
            init_sparsity: 0.1
            final_sparsity: 0.5
            targets: __ALL_PRUNABLE__

    quantization_modifiers:
        QuantizationModifier:
            start_epoch: 25
            end_epoch: 30
            bits: 8
            targets: __ALL_PRUNABLE__
"""

recipe = Recipe.create_instance(recipe)

yaml_str = recipe.yaml()
# print(yaml_str)
# print("++"* 20)

recipe_2 = Recipe.create_instance(yaml_str)
recipe_2_yaml = recipe_2.yaml()
# print(recipe_2_yaml)

assert yaml_str.strip() == recipe_2_yaml.strip()

Note: tests on GHA will fail until equivalent sparsezoo diff https://github.com/neuralmagic/sparsezoo/pull/483 lands