ENT-3417: Added allow_non_convergent to pattern_matching promise in edit_line

[victormlg]

Added a new attribute allow_non_convergent in replace_pattern promise to allow for idempotent non-convergent regex.

bundle agent __main__
{
  files:
      "/tmp/example.txt"
        content => "bash PORT=23 echo";

      "/tmp/example.txt"
        edit_line => regex_replace( "PORT=[0-9]+", "PORT=22" );

}
# From the stdlib:
bundle edit_line regex_replace(find,replace)
# @brief Find exactly a regular expression and replace exactly the match with a string.
# You can think of this like a PCRE powered sed.
# @param find The regular expression
# @param replace The replacement string
{
  replace_patterns:

      "$(find)"
        replace_with => value("$(replace)"),
        comment => "Search and replace string",
        allow_non_convergent => "true";
}

body replace_with value(x)
# @brief Replace matching lines
# @param x The replacement string
{
        replace_value => "$(x)";
        occurrences => "all";
}

I am a bit ensure on the implementation, but the idea is that we don't want to allow destructive non-convergent regex, such as:

bundle agent __main__
{
  files:
      "/tmp/example.txt"
        content => "PORT=23";

      "/tmp/example.txt"
        edit_line => regex_replace( "PORT=[0-9]+", "PORT=22 #Some comment" );

}

This will replace and rematch the same line indefinitely:
PORT=22 #Some comment #Some comment #Some comment [...]

So the idea was to let cfengine match and expand the pattern N times (as before), then we match and expand one more time (N+1), and if the total length of the line is greater, this means that the non-convergent regex is destructive and thus we need to error.