Support Python 3.14 / Update Pydantic

[meeuw]

Python 3.14 has been released and I've tried running the build.yml workflow but it seems to fail with the following error message:

make pr
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.14.0/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/Python/3.14.0/x64/lib/pkgconfig
    Python_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64
    Python2_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/Python/3.14.0/x64
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.14.0/x64/lib
# Checking latest schema was generated (run `make schema` if this fails)
mkdir -p .tmp
python -m samtranslator.internal.schema_source.schema --sam-schema .tmp/sam.schema.json --cfn-schema schema_source/cloudformation.schema.json --unified-schema .tmp/schema.json
/home/runner/work/serverless-application-model/serverless-application-model/samtranslator/compat.py:2: UserWarning: Core Pydantic V1 functionality isn't compatible with Python 3.14 or greater.
  from pydantic import v1 as pydantic
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/runner/work/serverless-application-model/serverless-application-model/samtranslator/internal/schema_source/schema.py", line 10, in <module>
    from samtranslator.internal.schema_source import (
    ...<10 lines>...
    )
  File "/home/runner/work/serverless-application-model/serverless-application-model/samtranslator/internal/schema_source/aws_serverless_api.py", line 5, in <module>
    from samtranslator.internal.schema_source.aws_serverless_connector import EmbeddedConnector
  File "/home/runner/work/serverless-application-model/serverless-application-model/samtranslator/internal/schema_source/aws_serverless_connector.py", line 16, in <module>
    class ResourceReference(BaseModel):
    ...<7 lines>...
        Type: Optional[str] = resourcereference("Type")
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/main.py", line 221, in __new__
    inferred = ModelField.infer(
        name=var_name,
    ...<3 lines>...
        config=config,
    )
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/fields.py", line 504, in infer
    return cls(
        name=name,
    ...<7 lines>...
        field_info=field_info,
    )
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/fields.py", line 434, in __init__
    self.prepare()
    ~~~~~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/fields.py", line 555, in prepare
    self.populate_validators()
    ~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/fields.py", line 829, in populate_validators
    *(get_validators() if get_validators else list(find_validators(self.type_, self.model_config))),
                                              ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/site-packages/pydantic/v1/validators.py", line 768, in find_validators
    raise RuntimeError(f'no validator found for {type_}, see `arbitrary_types_allowed` in Config')
RuntimeError: no validator found for <class 'pydantic.v1.fields.UndefinedType'>, see `arbitrary_types_allowed` in Config
make: *** [Makefile:37: format-check] Error 1
Error: Process completed with exit code 2.

Pydantic V1 is not compatible with Python 3.14 and greater so I think the serverless-application-model need to update to Pydantic V2.