Add support to calculate distance between device and anchor and distance between two anchors

[dnkoulouris]

This pull request implements two functionalities that are required for many use cases:

• calculate distance from device to anchor
• calculate distance between two anchors

The distance is counted in meters and uses the Vector 3 square root method.
Method getCameraPose() that obtains device coordinates is required and was cloned from gps branch

Methods added in ar_session_manager.dart along with the required platform code in Swift and Kotlin:

• getPose(ARAnchor anchor): Returns the given anchor pose in Matrix4 format with respect to the world coordinate system of the ARView.
• getDistanceBetweenAnchors(ARAnchor anchor1, ARAnchor anchor2): Returns the distance in meters between @anchor1 and @Anchor2.
• getDistanceFromAnchor(ARAnchor anchor): Returns the distance in meters between @anchor and device's camera.
• getDistanceBetweenVectors(Vector3 vector1, Vector3 vector2): Returns the distance in meters between @vector1 and @vector2.

[Petroni]

Tested out getDistanceFromAnchor and getDistanceBetweenAnchors on iOS and all seems to be working well without any issues. Currently in the process of testing on Android

[CariusLars]

Hey @dnkoulouris , thanks for the contribution! I left a few comments on your code but looks good otherwise, once @Petroni is done testing on Android and the comments are fixed I'm happy to merge :)

[Petroni]

2 Small issues on the Android side. AndroidARView.kt f line 108 & 116 are throwing errors due to being passing null values.
Managed to fix this from my end by passing an empty string instead of null.

[dnkoulouris]

So, what is the current status?

[dnkoulouris]

I also fixed the error that @Petroni mentioned in my fork

[CariusLars]

Hey folks, sorry for the late reply, I've been very busy the last couple of weeks..

@dnkoulouris thanks for the fix, could you reply to / fix the three review comments I left after your initial PR above? After that I´m happy to merge :)

[dnkoulouris]

@CariusLars I can not see your commits. In which branch/repo are they?

[CariusLars]

if you scroll up on this page you should see three review comments (they are not commits). I'v attached a screenshot below

[dnkoulouris]

Readme file reverted to the original state.
Concerning the Info.plist issue, according to this:
https://github.com/flutter/flutter/issues/94508
I added the flag to support higher frame rates in iPhone screens (iPhone 13 series).

[dnkoulouris]

I also made a commit that fixes this issue.
In this commit I included required dependency upgrades.

[CariusLars]

awesome, thanks @dnkoulouris! I merged this just now :)