config: Clone language map entries before modifying them

[bep]

Now, with YAML anchor and alias support, these can point to shared data,
which must not be modified in place.

Fixes #14072

[Copilot]

Pull Request Overview

This PR fixes issue #14072 by preventing in-place modification of shared configuration data that can occur with YAML anchors and aliases. The solution involves deep-cloning language map entries before modification.

• Introduces CloneParamsDeep function to recursively clone nested Params maps
• Adds cycle detection to SetParams via depth tracking
• Clones language configuration entries before merging to avoid modifying shared references

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
common/maps/params.go	Adds CloneParamsDeep function and refactors SetParams with cycle detection; removes shallow clone during merge
config/allconfig/allconfig.go	Clones language config entries before modification and removes now-redundant shallow clone
hugolib/config_test.go	Re-enables previously skipped test and increases test iteration count
common/hdebug/debug.go	Adds new debug utilities (unrelated to the main fix)

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