cabal: filtering GHC args

[coot]

This PR changes how cabal is normalising program flags. Instead of
normalising them for program invocation, it normalises them just for caching
purposes. This allows us to pass any GHC flag without cabal, surprisingly
removing it. This allows one to pass things like -freverse-errors,
-Rghc-timing, and many others.

I am not deeply familiar with cabal's codebase, so please excuse if I am doing something silly.

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• Patches conform to the coding conventions.
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[Copilot]

Pull Request Overview

This PR modifies Cabal's handling of program arguments (like GHC flags) to separate normalization for caching purposes from actual program invocation. Previously, Cabal normalized program flags for both purposes, which inadvertently filtered out valid GHC flags like -freverse-errors and -Rghc-timing. The change introduces a new field to store normalized arguments used only for hashing/caching, while preserving the original arguments for actual program execution.

Key changes:

• Introduced elabNormalisedProgramArgs field to store normalized program arguments for caching
• Modified normalization to only affect the new field, leaving elabProgramArgs unfiltered for execution
• Updated hash computation to use normalized arguments while program invocation uses original arguments

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
changelog.d/pr-11259.md	Added changelog entry documenting the removal of program argument filtering
cabal-install/src/Distribution/Client/ProjectPlanning/Types.hs	Added elabNormalisedProgramArgs field and updated normaliseConfiguredPackage to populate it instead of modifying elabProgramArgs
cabal-install/src/Distribution/Client/ProjectPlanning.hs	Initialized elabNormalisedProgramArgs during plan elaboration and updated hash computation to use normalized args

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[Copilot]

The elabNormalisedProgramArgs field is being initialized with the same logic as elabProgramArgs (lines 2382-2392), but it should be initialized with the result of normaliseConfiguredPackage applied to the original args. Currently, both fields contain identical unfiltered arguments at initialization, meaning normalization isn't actually happening. The normalized version should be computed after creating the package record by applying the lookupFilter logic from normaliseConfiguredPackage.