chore(LinearAlgebra/Ray): remove a defeq abuse

[wwylele]

Previously, the code uses Subtype constructor to construct RayVector, and the instance cannot see through this. As a common practice, RayVector declares its own constructor to resolve this

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[github-actions]

PR summary 1bac7ff38c

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ RayVector.coe_mk
+ RayVector.ext
+ RayVector.mk

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

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No changes to strong technical debt.

No changes to weak technical debt.