Add support for automatic updates

[autodidaddict]

Wash should check for newer versions of itself whenever it starts and, if it finds one, should automatically upgrade to that version. A corresponding wash update can be made available to perform a manual check / verbose update.

Not sure if this will "play nice" with versions of wash that were installed via packagecloud/etc, but the one thing that we should never force our developers to do is figure out how to manually upgrade wash after they've been using it for a while. Once it's on their machine, it should always be the newest version.

[autodidaddict]

For reference, here's some output from the Haskell CLI stack, where I've typed stack upgrade and it automatically did everything I needed, including switching to sudo since I forgot to do it myself. I think one problem I have as someone with multiple operating systems and a metric ton of installed software is I don't remember how I installed everything that I have, so if I can just wash upgrade, that means I don't have to remember if I used a brew port or apt or snap or if I manually installed it from a GH release binary, etc.

stack upgrade
Current Stack version: 2.1.3, available download version: 2.5.1
Newer version detected, downloading
Querying for archive location for platform: linux-x86_64-static
Querying for archive location for platform: linux-x86_64
Downloading from: https://github.com/commercialhaskell/stack/releases/download/v2.5.1/stack-2.5.1-linux-x86_64.tar.gz
Download complete, testing executable
Version 2.5.1, Git revision d6ab861544918185236cf826cb2028abb266d6d5 x86_64 hpack-0.33.0
New stack executable available at /home/kevin/.local/bin/stack
Also copying stack executable to /usr/local/bin/stack
Permission error when trying to copy: /usr/local/bin: copyFile:atomicCopyFileContents:withReplacementFile:openBinaryTempFile: permission denied (Permission denied)
Should I try to perform the file copy using sudo? This may fail
Try using sudo? (y/n) y
Going to run the following commands:

-  sudo cp /home/kevin/.local/bin/stack /usr/local/bin/stack.tmp
-  sudo mv /usr/local/bin/stack.tmp /usr/local/bin/stack
[sudo] password for kevin: 

sudo file copy worked!

[stale[bot]]

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