Bugfix: honor upstream default for enableDynamicPortAllocation

[dark]

Having a hardcoded default_value of false for the
enableDynamicPortAllocation property is troublesome, and the
upstream default should be used. This was added as part of #6022.

By hardcoding the default here, any client will explicitly deprogram
the dynamic port allocation setting if it is not part of the client
configuration. This is causing problems for those clients that have
enabled the dynamic port allocation out of band, since the current
support is incomplete (not all parameters can be set via Terraform:
terraform-google-modules/terraform-google-cloud-nat#64 (comment)). While
full support is being added, removing hardcoded defaults allow
out-of-band configurations to continue working.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

compute: fix default handling for `enableDynamicPortAllocation` to be managed by the api

[modular-magician]

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[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 1 deletion(-))
TF Validator: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))

[modular-magician]

Tests analytics

Total tests: 2048
Passed tests 1819
Skipped tests: 226
Failed tests: 3

Action taken

Triggering VCR tests in RECORDING mode for the tests that failed during VCR. Click here to see the failed tests

TestAccFirebaserulesRelease_BasicRelease|TestAccContainerCluster_withConfidentialNodes|TestAccContainerCluster_withAddons

[modular-magician]

Tests passed during RECORDING mode:
TestAccFirebaserulesRelease_BasicRelease[view]

Tests failed during RECORDING mode:
TestAccContainerCluster_withAddons[view]
TestAccContainerCluster_withConfidentialNodes[view]

Please fix these to complete your PR
View the build log or the debug log for each test

[ScottSuarez]

in the .terraform file alongside the api file could you add default from api to this field?

[dark]

Sure! Done.

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
TF Validator: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))

[modular-magician]

Tests analytics

Total tests: 2048
Passed tests 1819
Skipped tests: 226
Failed tests: 3

Action taken

Triggering VCR tests in RECORDING mode for the tests that failed during VCR. Click here to see the failed tests

TestAccFirebaserulesRelease_BasicRelease|TestAccContainerCluster_withConfidentialNodes|TestAccContainerCluster_withAddons

[modular-magician]

Tests passed during RECORDING mode:
TestAccFirebaserulesRelease_BasicRelease[view]

Tests failed during RECORDING mode:
TestAccContainerCluster_withAddons[view]
TestAccContainerCluster_withConfidentialNodes[view]

Please fix these to complete your PR
View the build log or the debug log for each test