Tests requiring the `conftest` binary fail with newer versions of the utility

[tpickett66]

When running the tests on a fresh system the following failure occurs:

--- FAIL: TestGitHubWorkflowWithPolicyCheck (0.03s)
    events_controller_e2e_test.go:1324: conftest >= 0.25.0 must be installed to run this test
FAIL
FAIL	github.com/runatlantis/atlantis/server/controllers/events	131.108s
FAIL

When the latest version of conftest (0.34.0) is installed using homebrew this failure persists despite the binary being on $PATH. Digging into the code I found that the tests are looking for a binary named conftest0.25.0, adding a symlink with this name allowed the tests to find the binary but they still fail with a different error.

» go test ./server/controllers/events
--- FAIL: TestGitHubWorkflowWithPolicyCheck (0.13s)
    events_controller_e2e_test.go:1335: could not parse contest version from Conftest: 0.34.0
        OPA: 0.43.0
FAIL
FAIL	github.com/runatlantis/atlantis/server/controllers/events	138.859s
FAIL

It seems like there are two problems here.

1. We're looking for a binary with a version in the name rather than the generic binary name
2. The version detection logic checking the program output is not handling the new output correctly.

[nitrocode]

Hmm then perhaps we need to update this version or change the logic so we can avoid this check. I'm unsure how much value a version check is doing here.

atlantis/server/controllers/events/events_controller_e2e_test.go

Line 44 in 3bfd769

const ConftestVersion = "0.25.0"

atlantis/server/core/runtime/policy/conftest_client_test.go

Line 25 in 90e92e3

version, _ := version.NewVersion("0.25.0")

But perhaps it's simply testing downloading custom versions of conftest? Would you be able to look at this closer @tpickett66 ?