Delete DEFAULT_STACK_SIZE

[MichalStrehovsky]

#110455 (comment)

[Copilot]

Pull Request Overview

This PR removes the deprecated DEFAULT_STACK_SIZE property bag functionality from the CoreCLR runtime. The change eliminates legacy code that parsed stack size configuration through the host property bag mechanism.

• Removes the ParseDefaultStackSize function and related static variable
• Eliminates property bag parsing for DEFAULT_STACK_SIZE in the host creation process
• Simplifies stack size determination to use only environment variables and configuration values

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/coreclr/vm/threads.cpp	Removes ParseDefaultStackSize function, static variable, and simplifies GetDefaultStackSizeSetting logic
src/coreclr/vm/corhost.cpp	Removes property bag parsing for DEFAULT_STACK_SIZE during app domain creation

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[am11]

LGTM, I thought we had an environment variable called DEFAULT_STACK_SIZE, but this is actually the name used in property bag for hosting layer. (It was anyway irrelevant for public doc since environment var can't influence the value)