`api.MockJob` is a test utility, that's only used by `command/agent`
package.  This moves it to the package and removes it from the public
API.

nomad/structs is an internal package and imports many libraries (e.g.
raft, codec) that are not relevant to api clients, and may cause
unnecessary dependency pain (e.g. `github.com/ugorji/go/codec`
version is very old now).

Here, we add a code generator that imports the relevant constants from
`nomad/structs`.

I considered using this approach for other structs, but didn't find a
quick viable way to reduce duplication.  `nomad/structs` use values as
struct fields (e.g. `string`), while `api` uses value pointer (e.g.
`*string`) instead.  Also, sometimes, `api` structs contain deprecated
fields or additional documentation, so simple copy-paste doesn't work.
For these reasons, I opt to keep the status quo.

client: restore Terminated event on every exit

Fix typo in PluginLoader

Some Windows fixes and CI

Fix one more place that should be using taskResources

taskResources handles new resource fields in a backwards compatible way

v0.9.0-dev started emitting a Terminated event every time a task process
exited. While this wasn't true in previous versions, it's a useful task
event because it's the only place for job operators to view the task's
exit code.

This behavior is asserted in the e2e/taskevents tests.

Co-Authored-By: dantoml <dani@tomlinson.io>

Co-Authored-By: dantoml <dani@tomlinson.io>

Co-Authored-By: dantoml <dani@tomlinson.io>

Due to https://github.com/tsenart/deadcode/issues/3 we can't specify
these consts on their own. This moves them into the _platform_test.go
files to avoid creating a package that only exposes a couple of values.

* Docker for Windows does not support ulimits
* Use filepath.ToSlash to test workdir
* Convert expected mount paths to system style
* Skip security-opt test on windows
  - Windows does not support seccomp, and it's unclear which options are
    available.
* Skip StartN due to lack of sigint
* docker: Use api to get image info on windows
* No bridge on windows
* Stop hardcoding /bin/

Uses the home directory and windows path expansion, as c:\tmp doesn't
necessarily exist, and mktemp would involve unnecessarily complicating
the commands.

This validates the slash variant of a RelativeDest, rather than the
platform native version, to support test execution on windows.