Fix Copy as cURL omitting headers and body on failed requests

[muhammadkamel]

Summary

• Copy as cURL from the Network profiler dropped request headers and body when the HTTP response never completed (timeouts, connection errors, cancelled POSTs).
• The generated command was only curl --location --request POST 'url' even though the app had sent JSON and headers.
• Fetch full profile data before copying, keep request headers/body when no response arrives, and cover this with unit tests.

This is a Network profiler bug found while copying a timed-out POST from DevTools. There is no open issue for the missing body; related history: #3042 (original Copy as cURL), #9828 (copy request like the browser).

Test plan

• flutter test packages/devtools_app/test/http/curl_command_test.dart
• flutter test packages/devtools_app/test/screens/network/network_model_test.dart
• In DevTools Network: Copy as cURL on a completed POST includes --header and --data-raw
• Copy as cURL on a timed-out / failed POST still includes body/headers when the VM profile recorded them
• Copy as URL is unchanged

Pre-launch Checklist

General checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I updated/added relevant documentation (doc comments with ///).

Issues checklist

• I listed at least one issue that this PR fixes in the description above.
• I listed at least one issue which has the contributions-welcome or good-first-issue label.
• I did not list at least one issue with the [contributions-welcome] or [good-first-issue] label. I understand this means my PR might take longer to be reviewed.

Tests checklist

• I added new tests to check the change I am making...
• OR there is a reason for not adding tests, which I explained in the PR description.

AI-tooling checklist

• I did not use any AI tooling in creating this PR.
• OR I did use AI tooling, and...
  • I read the AI contributions guidelines and agree to follow them.
  • I reviewed all AI-generated code before opening this PR.
  • I understand and am able to discuss the code in this PR.
  • I have verifed the accuracy of any AI-generated text included in the PR description.
  • I commit to verifying the accuracy of any AI-generated code or text that I upload in response to review comments.

Feature-change checklist

• This PR does not change the DevTools UI or behavior and...
  • I added the release-notes-not-required label or left a comment requesting the label be added.
• OR this PR does change the DevTools UI or behavior and...
  • I added an entry to packages/devtools_app/release_notes/NEXT_RELEASE_NOTES.md.
  • I included before/after screenshots and/or a GIF demo of the new UI to my PR description.
  • I ran the DevTools app locally to manually verify my changes.

[gemini-code-assist]

Code Review

This pull request enhances the "Copy as cURL" feature in the network profiler to include request headers and bodies for failed, timed-out, or cancelled requests, and adds corresponding tests. The review feedback identifies two critical areas where asynchronous calls to getFullRequestData() using unawaited could lead to unhandled exceptions, recommending the use of try-catch blocks or .catchError to handle potential errors gracefully.