Add a command to ignore checking updates on bot's startup

### What component of Red (cog, command, API) would you like to see improvements on?

Core

### Describe the enhancement you're suggesting.

I've been kind of spammed by my bot each time I had to reboot my Raspberry Pi which host multiple things, and also a Red instance, however I am not interested to update my Red instance for a patch update (3.4.12 -> 3.4.14 in my case), and it made me thought, "Wouldn't it be nice to be able to ignore update checks everytime my bot start?"

Any modern program of today usually allow you to either ignore this specific version or ignore all new versions. I think it would be great if we add a command that would make Red ignore update checking. As I can think off, `[p]ignorecheckupdates`.

### Anything else?

I think the command I am proposing could have 2 ways to be used:

### 1st proposition
The command has the following syntax: `[p]ignorecheckupdates`.
When we run it, the command will ask how do we want to ignore new updates, like this:
 (Text is NOT final)
### 2nd proposition
The command has the following syntax: `[p]ignorecheckupdates [choice]`.
The docstring will contain pretty much the same explainations like above, it'll simply just not be a MessagePredicate anymore.