.arcconfig

import-checker: use testparseutil.embedded() to centralize detection logic

This patch fixes issues of embedded() in import-checker.py below, too.

  - overlook (or mis-detect) the end of inline script in doctest style

  - overlook inline script in doctest style at the end of file
    (and ignore invalid un-closed heredoc at the end of file, too)

  - overlook code fragment in styles below
    - "python <<EOF" (heredoc should be "cat > file <<EOF" style)
    - "cat > foobar.py << ANYLIMIT" (limit mark should be "EOF")
    - "cat << EOF > foobar.py" (filename should be placed before limit mark)
    - "cat >> foobar.py << EOF" (appending is ignored)

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}