Model 5 fixer configs in blink instead of ignoring them

[TomasVotruba]

Problem

A blink run on an ECS config reports some rules as:

blink: 5 configured ECS rule(s) applied with blink's built-in behaviour (config not modelled):
    - PhpCsFixer\Fixer\ClassNotation\ModifierKeywordsFixer
    - PhpCsFixer\Fixer\Import\SingleImportPerStatementFixer
    - PhpCsFixer\Fixer\LanguageConstruct\NullableTypeDeclarationFixer
    - PhpCsFixer\Fixer\NamespaceNotation\BlankLinesBeforeNamespaceFixer
    - PhpCsFixer\Fixer\Operator\OperatorLinebreakFixer

These 5 fixers did not implement ConfigurableFixer, so their options (even the resolved defaults php-cs-fixer dumps) were dropped and reported as ignored.

Change

Each fixer now implements ConfigurableFixer and honors its php-cs-fixer options:

• modifier_keywords: elements subset (const / property / method)
• single_import_per_statement: group_to_single_imports - the default (true) now expands brace group imports use A\{B, C};; false keeps the group
• nullable_type_declaration: syntax: union rewrites ?T to T|null
• blank_lines_before_namespace: min_line_breaks / max_line_breaks
• operator_linebreak: only_booleans and position: end

With these wired up, resolveECS resolves the config instead of adding them to ConfigIgnored.

Tests

Added a _config_test.go per fixer covering default and non-default options; full go test ./... passes.