Add wait commands and --no-wait support

[tjprescott]

Adds wait command for the following: express-route, local-gateway, vnet-gateway, vmss

Add --no-wait parameters to the following:
vm: create, delete, deallocate, generalize, stop, start, restart, redeploy, resize
vm user: update, delete, reset-ssh
vmss: create, delete, update, deallocate, delete-instances, stop, restart, start, update-instances, reimage, scale
vnet-gateway: delete
local-gateway: create, delete, update
express-route: create, delete, update

[codecov-io]

Codecov Report

Merging #2524 into master will decrease coverage by 0.06%.
The diff coverage is 83.09%.

@@            Coverage Diff             @@
##           master    #2524      +/-   ##
==========================================
- Coverage   72.09%   72.02%   -0.07%     
==========================================
  Files         362      362              
  Lines       19758    19764       +6     
  Branches     2909     2912       +3     
==========================================
- Hits        14244    14236       -8     
- Misses       4600     4610      +10     
- Partials      914      918       +4

Impacted Files	Coverage Δ
...etwork/azure/cli/command_modules/network/custom.py	61.62% <100%> (ø)	✅
...re-cli-vm/azure/cli/command_modules/vm/commands.py	90.47% <100%> (-1.74%)	❌
...work/azure/cli/command_modules/network/commands.py	98.98% <100%> (+0.01%)	✅
...zure-cli-vm/azure/cli/command_modules/vm/custom.py	73.82% <64.28%> (-0.69%)	❌
src/azure-cli-core/azure/cli/core/commands/arm.py	88% <80%> (-0.83%)	❌

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[yugangw-msft]

Left one question on 'generic update' logic, the rest LGTM

[yugangw-msft]

Shall we just say '{}' was not expected'. I don't know much about generic update though, but in case it helps
Also why we want to error out here? I assume we will apply their values on sending out the update payload?

[tjprescott]

There's an Action somewhere that removes the entries in these lists and puts them into the "ordered_args" argument. So if anything was left in these, I want to raise an error so I know there's a bug in the generic update logic before I delete them.

[troydai]

What's the cost of get_arguments_loader()? Can we call it once and save the result?

[tjprescott]

We are only calling it once in the handler. This method doesn't get the "argument_loader" in the sense that "get_foo" would get the foo. It returns the CLI Arguments for the "get" side of the update. There's a corresponding "set_arguments_loader" that returns the CLI Arguments for the "set" side of the update. That's also only called once in the handler.