[Swift] Optional Scalars Preparation

[mustiikhalil]

The following PR prepares the swift implementation to take optional scalars as a parameter. it adds two functions that swift users would find useful.

1- Optional scalars #6014

static func addInt(e: Int?) { builder.add(element: e, offset: VOffset.int.v) }
// which can be called by the generated code
SomeTable.addInt(e: nil)

2- Optional strings

// In the current swift implementation the following is required to add `String` optional values.
var offset: Offset<String>
if let e = someString {
   offset = builder.create(string: e)
} else {
  offset = Offset<String>()
}

// This is a helper method for swift since we would usually write the following:
var offset = builder.create(string: someString) // where someString can have a value or be simply nil

3- updates the version to 0.7.0 since adding optionals is a major update.

4- disable linters in the generated code

@aardappel what do you think? would an optional string helper function be useful in other languages too? should I add it?

[aardappel]

In languages where a string can legally be null, return a 0 offset would be a good idea that can be part of the regular CreateString. This is not the case in all languages, for example a C++ std::string cannot be null.

Not sure about the optional ints, maybe wait until the first flatc for that has landed?

[mustiikhalil]

Yeah, that makes complete sense, JavaScript, maybe also csharp, and go. After all this is a nice to have.

Yes, this is just a draft for now until flatc supports it, so we can simple write the generator code for swift later on. Which would be cpp related and not swift.

[mustiikhalil]

@aardappel I've moved this to ready to merge incase we would want to merge this PR for now, and then start working on the cpp generator to work with optional values

[aardappel]

Ok, you can merge this now. Though would be good in the future to keep unrelated topics in separate PRs (small unrelated fixes / improvements are ok, but larger ones in their own PR I'd say).

[mustiikhalil]

Noted