fix: throw valid error when missing required params

[cristiand391]

What does this PR do?

This PR brings back the validateFlags logic to source:deploy and source:manifest:create commands.
There's a current bug in oclif that makes sfdx print an invalid error message when using the exactlyOne prop in flags:

sfdx force:source:deploy
ERROR running force:source:deploy:  Exactly one of the following must be provided: m,a,n,i,f,e,s,t

sfdx force:source:manifest:create
ERROR running force:source:manifest:create:  Exactly one of the following must be provided: m,e,t,a,d

I've openen a PR in oclif/core but until it's merged/we migrate to core, this should work.

What issues does this PR fix or reference?

@W-0@