Update LDE Node Pool Assertion and Test env variable Handling

[ykim-akamai]

📝 Description

Address assertion failure, changed it to be more flexible asserting if lde has an explicitly set value upon cluster creation

Now makefile uses LINODE_ env vars if set, falls back to TEST_ if not, and finally uses hardcoded defaults when neither is available — making the setup more consistent with other repositories

✔️ How to Test

Test environment variables:

# run it against alpha or staging
unset TEST_API_URL TEST_API_VERSION TEST_API_CA
export LINODE_TOKEN="token"
export TEST_API_URL="https://api.dev.linode.com" 
export LINODE_API_VERSION="v4beta"
export LINODE_CA="/tmp/test_ca.pem"

make test-int TEST_SUITE=api_request_basic

# unset these test vars
unset LINODE_API_URL LINODE_API_VERSION LINODE_CA

export LINODE_API_TOKEN="alpha_token"
export TEST_API_URL="https://api.dev.linode.com/"
export TEST_API_VERSION="v4beta"
export TEST_API_CA="/tmp/test_ca.pem"

make test-int TEST_SUITE=api_request_basic

Test LKE assertion changes:

make TEST_SUITE="lke_cluster_basic" test-int 
 make TEST_SUITE="lke_node_pool_basic" test-int

📷 Preview

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[lgarber-akamai]

Tests are passing on my end. Great quality of life improvement and nice work!