Disable IRQs on RP2040 during HW division

[earlephilhower]

The divider is a shared HW resource, and when an IRQ comes in (i.e. when a packet is processed by LWIP and the user's callbacks) its state can be corrupted silently and randomly.

Change the Pico-SDK defaults to disable IRQs during division operations, avoiding the issue by disallowing the LWIP callback to happen until after division is completed.

Fixes #3212

[yohine]

I found the real cause. The 64-bit timer loop is unrelated to the WiFi library. There is nothing wrong with Arduino library and SDK. The WiFi reconnection issue is resolved in #3212.

Sorry, I made it extra work for you here.

[yohine]

I'm currently running stability tests on my environment, applying 5.4.3 and update #3250. Operation under the same conditions as the previous task appears to be fine for now. It's too early to draw any conclusions about long-term stability, but I'll report any issues later.

I also performed another test: the stability of the WiFi library in an RP2040 multi-core environment.

In projects of a complexity involving SPI and I2C access, multi-core and WiFi are extremely unstable, even without an OS. I have not been able to get WiFi to work on multi-core with update #3250.

However, even if it can't be resolved, it's not a problem. When I started my project, the library was still version 5.2.0 or earlier, and even WiFi.beginNoBlock would block for several seconds. Therefore, I considered separating WiFi initialization on multi-core to avoid blocking the main task.

The blocking issue was resolved with an update to #3157 CYW43shim.cpp, and now begin itself does not block. Therefore, multi-core operation is no longer required.