remove SelectableText and make text selectable by default on web

[nt4f04uNd]

i'm proposing that:

1. any text would be selectable by default on web
2. SelectableText should be removed - this should be a parameter selectable in TextStyle and Text should support being selectable out of the box. while SelectableText will be deprected it should support being not selectable as well, so the TextStyle selectable applied would be respected

motivation of those:

1. users and developer expect that text is selectable on web
2. current sepration between Text and SelectableText creates a lot of pain:
   • there's no way to easilty tweak whether text is selectable or not
   • some of the created widgets that didn't add an ability to have a selectable text (which are i guess 99%) limit developers, and not only in framework, same applies to their own written widgets and packages

original issue #32246

In Flutter, text isn't selectable by default. Try using SelectableText to enable selection of text. Please let us know if you face any issues.

this answer is weird and recieved a lot of backlash in the comments below, but the issue never was reopened

cc @mdebbar @ferhatb @dnfield

[yjbanov]

This is not web-specific, so removing the web label. We'll need to decide whether controlling selectability outside the widget is a good idea.

[dnfield]

I'm somewhat partial to the idea of making selectable a bool property on text. It might also be neat to have an inherited widget that could control it's default too.

@LongCatIsLooong @chunhtai @justinmc wdyt?

[chunhtai]

We have talked about multi widget selection too, cc @HansMuller
The issue with the current text selection is that text selection is tightly coupled with text editing. It may requires a big refactoring or implementing a new selection system from scratch.

[justinmc]

Somebody, I think @HansMuller, brought it to my attention that Jetpack Compose uses a pattern similar to the inherited widget idea to enable selection in a subtree (docs). That's probably my favorite idea so far.

However, +1 to what @chunhtai said about this being a major project.