HTTP WRITE support

[lmangani]

This (humble) PR implements basic write (POST) support for the HTTPFS extension - similarly to the S3 features.

The implementation is intentionally simple, extending existing methods without introducing new dependencies.
The scope can be extended to be generally compatible with Web APIs when it comes to file management.

The current validation uses a very generic and simple backend service handling vanilla GET/POST requests and generally compatible with the ClickHouse url function, with nothing special to it. The demo backend is also deployed in public and open for testing, where the /path is the unique key to set/get data.

--- For backwards compatibility, WRITE support is disabled by default
D SET enable_http_write = 1;

--- COPY to remote servers using FORMAT
D SET enable_http_write = true;
D COPY (SELECT version() as version, 9999 as number) TO 'https://duckserver.glitch.me/.json' (FORMAT JSON);
D SELECT * FROM read_json_auto('https://duckserver.glitch.me/test9999');
┌─────────┬────────┐
│ version │ number │
│ varchar │ int64  │
├─────────┼────────┤
│ v1.1.0  │   9999 │
└─────────┴────────┘

--- COPY to remote servers using FORMAT auto-detection via extension
D COPY (SELECT version() as version, 9999 as number) TO 'https://duckserver.glitch.me/test.parquet';
D SELECT * FROM read_parquet('https://duckserver.glitch.me/test.parquet');
┌─────────┬────────┐
│ version │ number │
│ varchar │ int64  │
├─────────┼────────┤
│ v1.2.0  │   9999 │
└─────────┴────────┘

D SELECT * FROM parquet_schema('https://duckserver.glitch.me/test.parquet');
┌──────────────────────┬───────────────┬────────────┬─────────────┬───┬────────────────┬───────┬───────────┬──────────┬──────────────┐
│      file_name       │     name      │    type    │ type_length │ … │ converted_type │ scale │ precision │ field_id │ logical_type │
│       varchar        │    varchar    │  varchar   │   varchar   │   │    varchar     │ int64 │   int64   │  int64   │   varchar    │
├──────────────────────┼───────────────┼────────────┼─────────────┼───┼────────────────┼───────┼───────────┼──────────┼──────────────┤
│ https://duckserver…  │ duckdb_schema │            │             │ … │                │       │           │          │              │
│ https://duckserver…  │ version       │ BYTE_ARRAY │             │ … │ UTF8           │       │           │          │              │
│ https://duckserver…  │ number        │ INT32      │             │ … │ INT_32         │       │           │          │              │
├──────────────────────┴───────────────┴────────────┴─────────────┴───┴────────────────┴───────┴───────────┴──────────┴──────────────┤
│ 3 rows                                                                                                        11 columns (9 shown) │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

[lmangani]

Reopening since this is now a separate extension, hoping for a lower entry barrier and avoiding yet another fork of the extensions such as the caching one, etc. Work is in progress to enable compatibility with other extensions in the ecosystem.