HTTP: RPC / REST
----------------

The HTTP server has been rewritten from scratch to replace libevent. (#35182)

The `libevent` logging category has been removed. Configurations like
`-debug=libevent` or `-debugexclude=libevent` will log a deprecation warning
and be ignored. These configurations will result in an error in a future release.

Certain HTTP edge cases will observe different behavior to be more RFC-compliant:

- Stricter enforcement of maximum headers size (8192 bytes)
- Reject requests with whitespace in header field-names
- "Line Folding" is rejected (whitespace at start of a header line)
- Tolerate `%` at the end of requested URLs
- Multiple "Content-Length" headers with different values are rejected

A new configuration option `-rpcmaxconnections` (default `16`) limits the
number of simultaneously connected HTTP clients to the server. The application
will now attempt to reserve file descriptors for the HTTP server sockets. If your
system has limited resources, consider using a lower setting.