e1: highlight outdated extension versions (fix logic)

[NikolayS]

It is incorrect to compare pg_available_extensions.installed_version to pg_extension.extversion, it should be compared to pg_available_extensions.default_version. It led to incorrectly working actuality flag – at all times it was empty.

This commit fixes it. Also, available_extension column is removed – its logic was wrong from the very beginning.

Example:

• before fix:

      name        | installed_version | default_version | available_version | actuality
  --------------------+-------------------+-----------------+-------------------+-----------
  pg_stat_statements | 1.2               | 1.4             | 1.2               |
  plpgsql            | 1.0               | 1.0             | 1.0               |
  (2 rows)

• after fix:

      name        | installed_version | default_version | actuality
  --------------------+-------------------+-----------------+-----------
  pg_stat_statements | 1.2               | 1.4             | OLD
  plpgsql            | 1.0               | 1.0             |
  (2 rows)

[Nastradamus]

Neat. Do we need to fill actuality with something if everything is ok? E.g., following example looks slightly empty:

  name   | installed_version | default_version | actuality
---------+-------------------+-----------------+-----------
 plpgsql | 1.0               | 1.0             |
 plsh    | 2                 | 2               |
(2 rows)

[NikolayS]

@Nastradamus I've renamed the column to is_old

[Nastradamus]

@NikolayS should we use true or false as a required value for this column (id_old)?

[NikolayS]

@Nastradamus here we come to the question, what is better for humans and what is better for "robots". The current way how it's implemented -- it's better for humans. If "it is not old", we don't see anything in the column (if NULLs representation is not tuned in psql), and easily catch "OLD" rows.

For robots, it would be more appropriate to have true/false, yes.