[ADD]: Generic Matrix<T> 2D Array Type to Kotlin Standard Library

[krishpranav]

Description:

new class Matrix<T> to the Kotlin Standard Library under kotlin.collections, providing idiomatic, type-safe 2D array support for Kotlin developers. While Kotlin offers powerful tools for 1D arrays and collection APIs, native 2D array support has been a long-requested feature

Issue:

• https://youtrack.jetbrains.com/issue/KT-1140/Support-a-2D-array-type

Features:

• Generic, type-safe 2D structure: Matrix<T>
• Backed by a flat 1D array for memory and cache efficiency
• Intuitive access via matrix[row, col] using operator overloading
• Full bounds checking with informative errors
• Clear and concise implementation with extensibility in mind
• Designed for performance without sacrificing Kotlin idioms

[fzhinkin]

@krishpranav is there a particular use-case for the proposed API? As of now the implementation does almost nothing except providing 2D-addressing to elements and it is not clear how it could be used to solve practical problems which usually require matrices.

If you believe that it is a time to add a matrix API into the stdlib, please hit the YT issue (KT-1140) and describe your use cases, so it could be considered.

In the current form this PR will not be accepted. There are a few issues with code itself (no tests were added, lack of samples in the documentation, outdated Kotlin version in @SinceKotlin, to name a few), but that is something that could be fixed. The main blocker is that the API itself needs to be designed and discussed first (you can check other posted proposals to get a sense of how it works).