refactor: replace command inputs and options by a dictionary-like high-level data abstraction

[micalevisk]

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PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior?

I notice that all operations on command's inputs and options are using .find() to search for the first input/option found

What is the new behavior?

replace the usage of Input[] from .command.ts and .action.ts files by a new abstraction called CommandContext which hides the complexity of registering and retrieving some input/operation in a command lifecycle.

this change is intended to improve:

• code readability
  Instead of having a bunch of calls like inputs.find((o) => o.name === 'foo') we now have just one inputs.resolveInput('foo'), which is also slightly fast as it uses JS Map under the hood. This make it even clear that we shouldn't be define the same input name more than one time. I didn't write a validation for this scenario for [micro]performance sake but we could easily introduce that if needed
• type safety
  Instead of relying on type assertion and non-null assertions, we're using generics to make the code less error prone at compile time. The present solution doesn't differ that much from type assertions but there is a room to improve that easily by now

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[kamilmysliwiec]

I'd love to finally get rid of these confusing Input/Option abstractions - these are leftovers from the first version of the CLI 😄

[micalevisk]

in order to try this version better, I've published this branch's version as
micalevisk-nestjs-cli package. I've tested all the commands (but not all the flags, of course)