update terraform SDK to 2.4.0 and Nomad to 1.0.2

[cgbaker]

also, updated to 2.1.0 SDK. this caused a bunch of errors in the provider to become apparent, so we cleaned those up. numerous fields listed in the schema were never actually set, and have been removed.

[lgfa29]

I update the SDK version to 2.4.0 since this PR has been waiting for review for a while. I also updated Nomad to 1.0.1.

I also ran a quick test to make sure that the changes to the nomad_job resource wouldn't impact existing jobs. I used the Nomad E2E test suite but deployed the jobs using TF with the current released version of the provider (1.4.11).

I then updated my config to use a custom build from this PR and ran terraform apply again. There were no significant differences between in the state diff.

One group disappeared, but I think that was part of the test, and one volume switched from read_only = true to read_only = false, but I think that's because my environment didn't have the specific CSI plugin properly setup. Other volumes kept their read_only state.

[lgfa29]

Blocking this one for now because it modifies the schema of mount_options in nomad_volume in a way that will conflict with #188