Add services-xml fixer to convert Symfony services.xml to services.yaml

[Soner (shyim)]

The extension validator already warns about deprecated services.xml
files (Symfony deprecated the XML configuration format in 7.4 and
removes it in 8.0) but pointed users to an external tool for the
conversion.

This adds a new internal/symfony package that parses Symfony
services.xml files and emits the equivalent services.yaml, covering
parameters, imports, service definitions (all argument types, tags,
calls, factories, configurators, decoration, deprecation, properties,
bindings), defaults, prototypes, instanceof conditionals, aliases,
inline services and when@env blocks. The conversion refuses anything it
cannot represent instead of silently dropping configuration, keeping
the XML file untouched in that case.

A new "services-xml" verifier tool runs the conversion during
"shopware-cli extension fix" and "shopware-cli project fix" for
platform plugins, including extra bundles and locally imported XML
files (import resources are rewritten to the converted YAML files).
The validation message now points to the built-in fixer.

The generated YAML was verified to be semantically equivalent to the
XML by loading both into Symfony 7.4 ContainerBuilders and comparing
the resulting definitions, aliases and parameters.

https://claude.ai/code/session_014UNSrY9MntZK4VAthDwrTk

[github-code-quality]

Code Coverage Overview

Languages: Go

Go / code-coverage/go-test

The overall coverage in the claude/trusting-john... branch is 53%. The coverage in the main branch is 50%.

Show a code coverage summary of the most impacted files.

File	main f3a6da0	claude/trusting-john... 4f43031	+/-
internal/verifier/phpstan.go	17%	20%	+3%
internal/verifier/rector.go	4%	9%	+5%
internal/verifier/prettier.go	7%	14%	+7%
internal/verifi...r/phpcsfixer.go	7%	15%	+8%
internal/verifier/tool.go	60%	90%	+30%
internal/symfony/convert.go	0%	83%	+83%
internal/symfon...convert_file.go	0%	84%	+84%
internal/verifi...services_xml.go	0%	88%	+88%
internal/symfony/phpize.go	0%	94%	+94%
internal/symfon.../servicesxml.go	0%	96%	+96%

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reject null on-invalid references

When a service argument/property/call uses XML on-invalid="null", Symfony injects null when the target service is missing, but this conversion emits the YAML @? syntax, which is the ignore strategy. In method calls this changes behavior by removing the call instead of calling it with null (and Symfony documents that the null strategy is not supported by the YAML driver), so the fixer should refuse these XML references rather than silently rewriting them as ignore.

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[chatgpt-codex-connector]

Emit a YAML null for decoration-on-invalid

For XML decorators with decoration-on-invalid="null", this writes the string "null" into decoration_on_invalid. Symfony's YAML loader accepts an actual null value for this option and rejects the string "null", so converted files for that valid XML case fail to load after the fixer removes the original XML.

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