Add pattern matching support to Gem::Platform

[baweaver]

What was the end-user or developer problem that led to this PR?

Ruby 2.7+ introduced pattern matching, but Gem::Platform does not support it. This makes platform-specific conditional logic more verbose than necessary, particularly when routing gem installations or filtering platforms.

The current approach requires multiple conditionals or case statements with equality checks:

case platform
when Gem::Platform.new("x86_64-linux")
 install_linux_x64
when Gem::Platform.new("arm64-darwin")
 install_macos_arm
end

What is your fix for the problem, implemented in this PR?

Added deconstruct and deconstruct_keys methods to Gem::Platform to enable pattern matching syntax.

Implementation:

• deconstruct aliases the existing to_a method for array pattern matching, returning [cpu, os, version]
• deconstruct_keys returns a hash with keys :cpu, :os, and :version

This enables platform-based pattern matching:

case platform
in cpu: "x86_64", os: "linux"
 install_linux_x64
in cpu: "arm64", os: "darwin"
 install_macos_arm
end

Or extracting specific components:

platform in [cpu, os, version]
# cpu => "x86_64", os => "linux", version => nil

Make sure the following tasks are checked

• Describe the problem / feature
• Write tests for features and bug fixes
• Write code to solve the problem
• Make sure you follow the current code style and write meaningful commit messages without tags

[colby-swandale]

Similar to #9060, could we add a few lines of documentation to provide a quick explanation.

[baweaver]

Added