Add "Terraform: Apply" command

[kamilturek]

Closes #648.

Command terraform.apply is already registered so this PR only adds it to extension manifest.

vscode-terraform/src/extension.ts

Lines 66 to 68 in b5c8b6c

	vscode.commands.registerCommand('terraform.apply', async () => {
	await terraformCommand('apply', false, clientHandler);
	}),

[hashicorp-cla]

All committers have signed the CLA.

[jpogran]

Thanks @kamilturek for the contribution! Apologies on the delay in response, but we appreciate the help.

The reason we haven't surfaced the existing terraform apply command yet is that it will open the current terminal and just paste the command there. We haven't decided on the best UX here yet. If we enable it as is, it won't know if the command succeeded or failed, if terraform was on the path or not, if it was in the correct folder, etc.

What are your thoughts on this? While we discuss, I'm going to mark this as draft and put it on our planning board.