Allow command predicates to manage parameters, allow overwriting commands

[Guldoman]

Command predicates can now return more values after the command "validity" boolean. Those parameters are then passed to the actual commands.
Command predicates now also receive the parameters passed to command.perform.
This allows command predicates to manipulate or create from scratch the parameters that are passed to the actual commands.

command.add(function(x, y)
    return true, x + 1, y + 1
  end, {
  ["cmd:do-thing"] = function(x, y)
      print(x, y)
    end
  }
)

command.perform("cmd:do-thing", 1, 2) -- prints 2, 3

This also has the advantage of allowing to do heavy computations that are needed both by the predicate and the actual command only once.

command.add(function(a, b)
    local result = heavy_computation(a, b)
    return result.status == "OK", result
  end, {
  ["cmd:do-heavy-thing"] = function(heavy_result)
      do_thing_with(heavy_result)
    end
  }
)

command.perform("cmd:do-heavy-thing", a, b)

If a command predicate doesn't return any additional parameters, the original ones are passed through to the actual command.

command.add(function()
    return true
  end, {
  ["cmd:do-thing2"] = function(x, y)
      print(x, y)
    end
  }
)

command.perform("cmd:do-thing2", 1, 2) -- prints 1, 2

Now string and table predicates also return the active view. Additional parameters are also passed through.

local DocView = require "core.docview"

command.add("core.docview!", {
  ["cmd:do-thing-with-docview"] = function(dv, x, y)
      print(dv:is(DocView), x, y)
    end
  }
)

command.perform("cmd:do-thing-with-docview", 1, 2) -- prints true, 1, 2

---

Now when command.get_all_valid is called, each predicate is memoized to avoid recomputing it for each command that uses it.
This could be an important optimization for predicates that need heavy computations that are also used for multiple commands.

---

It's now possible to overwrite commands without errors.
While the assertion might have been useful to debug erroneous command overwrites, it also caused issues when saving the user module with commands defined inside it, as it resulted in the user-defined commands trying to overwrite themselves and failing.

---

As I changed many commands to use the new parameter passing, testing is needed as I might have missed something.

[jgmdev]

Are these missing dv replacements for doc() on purpose?

https://github.com/Guldoman/lite-xl/blob/PR_command_predicate_params/data/core/commands/doc.lua#L596-L619

[Guldoman]

Are these missing dv replacements for doc() on purpose?

https://github.com/Guldoman/lite-xl/blob/PR_command_predicate_params/data/core/commands/doc.lua#L596-L619

Totally forgot about them.

[jgmdev]

Tested and things seem to be working normally, merging.