Drop support for old Garfield versions

[lobis]

Recently we started supporting new versions of Garfield, which come with breaking changes. I made a few changes to the CMake and the code via preprocessor directives to support both versions, but recently @DavidDiezIb had some problems with the old version which means there is probably some unnoticed issue. I don't think its worth it to keep supporting these old versions, so I vote to just be compatible with the most recent version or a fairly recent one. (I would say latest tag, but currently this latest tag has a bug...).

rest-for-physics/framework@e58bdf4 removes the cmake file used to find the old Garfield and I will make the appropriate changes in this PR.

What do you think? @jgalan @nkx111 @juanangp

Related PR: #41 (review)

[nkx111]

I never tried the new version of Garfield. Will it make some difference to the drift speed simulated?

[lobis]

I never tried the new version of Garfield. Will it make some difference to the drift speed simulated?

I would say no, it would be interesting if someone can test this. We don't need to use the latest Garfield version, just a version that is not that old and has better CMake support. Our "official" version is like 5 years old or so if I remember correctly.

Anyway its really easy to update to a more recent Garfield version, there are not that many changes to the user API.