Style: Enforce separation line between function definitions

I couldn't find a tool that enforces it, so I went the manual route:
```
find -name "thirdparty" -prune \
  -o -name "*.cpp" -o -name "*.h" -o -name "*.m" -o -name "*.mm" \
  -o -name "*.glsl" > files
perl -0777 -pi -e 's/\n}\n([^#])/\n}\n\n\1/g' $(cat files)
misc/scripts/fix_style.sh -c
```

This adds a newline after all `}` on the first column, unless they
are followed by `#` (typically `#endif`). This leads to having lots
of places with two lines between function/class definitions, but
clang-format then fixes it as we enforce max one line of separation.

This doesn't fix potential occurrences of function definitions which
are indented (e.g. for a helper class defined in a .cpp), but it's
better than nothing. Also can't be made to run easily on CI/hooks so
we'll have to be careful with new code.

Part of #33027.

modules/mbedtls/stream_peer_mbedtls.cpp

@@ -141,6 +141,7 @@ Error StreamPeerMbedTLS::accept_stream(Ref<StreamPeer> p_base, Ref<CryptoKey> p_
 	status = STATUS_CONNECTED;
 	return OK;
 }
+
 Error StreamPeerMbedTLS::put_data(const uint8_t *p_data, int p_bytes) {
 	ERR_FAIL_COND_V(status != STATUS_CONNECTED, ERR_UNCONFIGURED);
 
@@ -267,6 +268,7 @@ int StreamPeerMbedTLS::get_available_bytes() const {
 
 	return mbedtls_ssl_get_bytes_avail(&(ssl_ctx->ssl));
 }
+
 StreamPeerMbedTLS::StreamPeerMbedTLS() {
 	ssl_ctx.instance();
 	status = STATUS_DISCONNECTED;