helper/resource: Added error logging before failing tests

[bflad]

Closes #956

If provider developers are using TF_ACC_LOG_PATH or TF_LOG_PATH_MASK, this will ensure that the separate log file will include the test failure reason, in addition to the test output.

Example from terraform-provider-corner, after purposefully breaking a check:

$ TF_ACC=1 TF_LOG=TRACE TF_ACC_LOG_PATH=test.txt go test -count=1 -run='TestAccFrameworkResourceUser$' -v ./internal/frameworkprovider
=== RUN   TestAccFrameworkResourceUser
    resource_user_test.go:12: Step 1/1 error: Check failed: Check 1/5 error: framework_user.foo: Attribute 'name' expected "Oops", got "Ford Prefect"
--- FAIL: TestAccFrameworkResourceUser (0.82s)
FAIL
FAIL    github.com/hashicorp/terraform-provider-corner/internal/frameworkprovider       1.162s

$ grep ERROR internal/frameworkprovider/test.txt
2022-05-04T14:42:58.636-0400 [ERROR] sdk.helper_resource: Unexpected error: test_name=TestAccFrameworkResourceUser test_step_number=1 test_terraform_path=/usr/local/bin/terraform test_working_directory=/var/folders/w8/05f3x02n27x72g0mc2jy6_180000gp/T/plugintest853754224 error="Check failed: Check 1/5 error: framework_user.foo: Attribute 'name' expected \"Oops\", got \"Ford Prefect\""

[bendbennett]

LGTM

[detro]

This makes sense.

[github-actions]

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