feat: http client for the http library

[algebraic-dev]

This PR adds a simple HTTP client for the HTTP library.

[leanprover-community-bot]

Mathlib CI status (docs):

• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase f9adafe54d5070acbd270643f71b8455ca8c8d68 --onto 41356740210745d6b9735cb779fbd0f9eee591e5. You can force Mathlib CI using the force-mathlib-ci label. (2025-11-23 15:25:33)
• ❗ Batteries/Mathlib CI will not be attempted unless your PR branches off the nightly-with-mathlib branch. Try git rebase f21f8d96f97989d3a34148329a158e94b220314b --onto 13c88f960f40b7c163b99e742010bbbbdbe8bba7. You can force Mathlib CI using the force-mathlib-ci label. (2025-12-24 17:09:00)

[leanprover-bot]

Reference manual CI status:

• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase f9adafe54d5070acbd270643f71b8455ca8c8d68 --onto d3dda9f6d4428a906c096067ecb75e432afc4615. You can force reference manual CI using the force-manual-ci label. (2025-11-23 15:25:34)
• ❗ Reference manual CI will not be attempted unless your PR branches off the nightly-with-manual branch. Try git rebase f21f8d96f97989d3a34148329a158e94b220314b --onto f317e28d842bad09a6111e1f72dda8a2c0bdc3c5. You can force reference manual CI using the force-manual-ci label. (2025-12-24 17:09:01)