Deprecate LSF option LSF_SERVER

[jonathan-eq]

Continuation of #7203 ert-configurations currently set LSF_SERVER to some ssh-able machine, and thus this is the dominant code path used in the current C driver.

Some komodo release must change this to activate the local shell before we move to the Python driver (that will only use the local shell). This change should be done with a warning, and for users getting into trouble, it should be possible for them to set LSF_SERVER in their config to reinstate the old behaviour.

Definition of done:

• ERT default is to use local shell for bsub/bjobs/bkill.
• Deprecation warnings are emitted while parsing the config, stating that these keywords have no effect and can safely be removed.
• Removal from documentation

The functionality will be gone from ERT whenever the legacy C LSF driver is purged.

[berland]

This issue should be blocked for at least two weeks after a stable release that does not use LSF_SERVER has been released