feat(#748): add test-with-comment lint

[VasilevNStas]

fix #748

What

A new tests/test-with-comment lint that warns when a test object has a
comment before it. A comment that duplicates the test name adds nothing —
the name should be self-explanatory.

How it works

The lint looks at top-level test objects (/object/o[eo:test-name(@name)],
i.e. +/- prefixed names). The parser puts the comment that precedes a
top-level object into /object/comments/comment. If a test object has any
such comment, a warning is reported.

Note: this only applies to top-level tests. A comment placed inside an
object right before a nested +> test is already a parse error
("comment is allowed only on top of the file, before metas"), so there is
no nested case to handle.

Why not the earlier attempt (PR #752)

The earlier PR #752 looked for meta[@key='comment'], but comments are not
stored as metas in XMIR — they live in /object/comments/comment. This
implementation uses the correct location.

Tests

• catches-test-with-comment — a comment before a top-level test is flagged
• allows-test-without-comment — no comment is clean

Both mvn test (592 tests) and mvn clean install -Pqulice pass.

[VasilevNStas]

@volodya-lombrozo @yegor256 please review this pull request

[yegor256]

@VasilevNStas comments are disabled in XMIR now, except the top-level single comment

[VasilevNStas]

@yegor256
Thanks — that is exactly the case this lint targets. Since nested comments are rejected by the parser, the only place a comment can appear is the top-level comment block (/object/comments/comment), right before the single top-level object. The lint flags precisely that: when the top-level object is a test (eo:test-name, i.e. +/- prefixed) and a top-level comment exists, it reports a warning. So it is aligned with the current XMIR behavior, not relying on any nested-comment support.