add create_facilitator_config for x402 python v2

[phdargen]

Description

Updates create_facilitator_config to support x402 python sdk v2:

• makes create_headers sync to support x402 v2 sdk release, see feat: New Python SDK with v2 support x402#841
• x402 legacy python sdk updated to support both sync and async create_headers in python-v2: make create_facilitator_config work with both V1 and V2 x402#968
• add auth headers for supported endpoint required for v2

Tests

Manually tested with modified v2 fastapi example by replacing:
facilitator = HTTPFacilitatorClient(FacilitatorConfig(url=FACILITATOR_URL))
with:

facilitator_config = create_facilitator_config(CDP_API_KEY_ID, CDP_API_KEY_SECRET)
facilitator = HTTPFacilitatorClient(facilitator_config)

Making request to: http://localhost:4021/weather

Response body: { report: { weather: 'sunny', temperature: 70 } }

Payment response: {
  success: true,
  payer: '0xE33A295AF5C90A0649DFBECfDf9D604789B892e2',
  transaction: '0x717dbc36b3ad908437c908ff96007073ccb54c1aaa8a270d28bca80cf5e9142b',
  network: 'eip155:8453'
}

Also tested with v1 mainnet example

Checklist

A couple of things to include in your PR for completeness:

• Updated the typescript README if relevant
• Updated the python README if relevant
• Added a changelog entry
• Added e2e tests if introducing new functionality

[cb-heimdall]

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