fix: preserve attribute call syntax in vfmt

[vincenzopalazzo]

What was broken

v fmt flattened call-style attributes like @[xml(name: 'foo')] into the older expanded form like @[xml_name: 'foo'].

Root cause

The parser normalized @[foo(...)] into multiple flat ast.Attr entries, but it did not preserve enough metadata for vfmt to know those attrs originally came from a single call-style attribute.

What changed

• preserved minimal call-style metadata on parsed attributes
• taught vfmt to re-emit grouped call syntax for top-level and inline attributes
• added formatter regression coverage for named args, positional args, unsafe(), and inline field attributes

Verification

• ./vnew -silent test vlib/v/fmt/
• ./vnew -silent test vlib/v/parser/
• ./vnew -silent test vlib/v/tests/comptime/comptime_attribute_call_syntax_test.v
• reproduced issue vfmt breaks the new attributes syntax #26766 locally with ./vnew fmt

Fixes #26766

[JalonSolov]

Close/re-open for CI run.