Make parsing from std::istream and FILE* fast (#5828)

* Make parsing from std::istream and FILE* fast

Squashed onto develop cd6b428ef (CI fixes from #5860). Original commits:

- Let the lexer's bulk fast paths run on a window of the input
- Scan the get area of an input stream in bulk
- Lock a FILE once per parse instead of once per character
- Add benchmarks for parsing from a FILE* and for many values from a stream
- Avoid implicit unsigned char to char conversion in stream tests
- Make file_input_adapter::unlock() safe to call on a moved-from adapter

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Add ABI tags for JSON_DISABLE_STREAM_BULK_SCAN and JSON_DISABLE_UNLOCKED_FILE_IO

Both macros select between two definitions of an input adapter, so
translation units compiled with different settings violated the ODR when
linked together. Like the other ABI-affecting macros, they now append a
tag to the inline namespace: _dsbs and _dufio. Their defaults move to
abi_macros.hpp so that json_fwd.hpp sees them, and the natvis file is
regenerated for the new namespaces.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Skip the exception-only checks of the stream input tests without exceptions

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/sax_parse.md

@@ -116,6 +116,10 @@ consumer `sax` has a super-linear complexity.
 
 A UTF-8 byte order mark is silently ignored.
 
+When reading from a `#!c FILE*`, the file is locked while it is parsed. The lock is recursive, so the SAX handler may
+use the same file with stdio functions, but it must not wait for another thread that uses the same `FILE` object; see
+[`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md).
+
 ## Examples
 
 ??? example
@@ -137,6 +141,10 @@ A UTF-8 byte order mark is silently ignored.
 
 - [parse](parse.md) - deserialize from a compatible input
 - [accept](accept.md) - check if the input is valid JSON
+- [`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md) - read a `std::istream` one character
+  at a time
+- [`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) - read a `FILE*` with the locking stdio
+  functions
 
 ## Version history
 
@@ -148,6 +156,10 @@ A UTF-8 byte order mark is silently ignored.
 - Extended overload (2) to accept heterogeneous iterator+sentinel pairs (C++20 ranges support) in version 3.13.0.
 - `JSON_PRECISE_STREAM_POSITION` added in version 3.13.0 to optionally leave a `#!cpp std::istream` positioned right
   after the parsed value when `strict` is `#!cpp false`.
+- Parsing from an `std::istream` scans the characters in its stream buffer in bulk in version 3.13.0
+  ([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
+- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
+  ([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
 
 !!! warning "Deprecation"