NIFI-7754: Support HTTP Proxy for JettyWebSocketClient

[xasx]

Thank you for submitting a contribution to Apache NiFi.

Please provide a short description of the PR here:

Description of PR

Enables HTTP Proxy support for WebSocket consumption; fixes bug NIFI-7754.

In order to streamline the review of the contribution we ask you
to ensure the following steps have been taken:

For all changes:

• Is there a JIRA ticket associated with this PR? Is it referenced
  in the commit message?

• Does your PR title start with NIFI-XXXX where XXXX is the JIRA number you are trying to resolve? Pay particular attention to the hyphen "-" character.

• Has your PR been rebased against the latest commit within the target branch (typically main)?

• Is your initial contribution a single, squashed commit? Additional commits in response to PR reviewer feedback should be made on this branch and pushed to allow change tracking. Do not squash or use --force when pushing to allow for clean monitoring of changes.

For code changes:

• Have you ensured that the full suite of tests is executed via mvn -Pcontrib-check clean install at the root nifi folder?
• Have you written or updated unit tests to verify your changes?
• Have you verified that the full build is successful on JDK 8?
• Have you verified that the full build is successful on JDK 11?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE file, including the main LICENSE file under nifi-assembly?
• If applicable, have you updated the NOTICE file, including the main NOTICE file found under nifi-assembly?
• If adding new Properties, have you added .displayName in addition to .name (programmatic access) for each of the new properties?

For documentation related changes:

• Have you ensured that format looks appropriate for the output in which it is rendered?

Note:

Please ensure that once the PR is submitted, you check GitHub Actions CI for build issues and submit an update to your PR as soon as possible.

[xasx]

Builds failed due to:

[ERROR] Failed to execute goal on project nifi-hwx-schema-registry-service: Could not resolve dependencies for project org.apache.nifi:nifi-hwx-schema-registry-service:jar:1.13.0-SNAPSHOT: 
Failed to collect dependencies at com.hortonworks.registries:schema-registry-client:jar:0.8.1 -> com.hortonworks.registries:common-auth:jar:0.8.1 -> com.nimbusds:nimbus-jose-jwt:jar:4.41.1 -> net.minidev:json-smart:jar:2.3-SNAPSHOT: Failed to read artifact descriptor for net.minidev:json-smart:jar:2.3-SNAPSHOT: 
Could not transfer artifact net.minidev:json-smart:pom:2.3-SNAPSHOT from/to apache.snapshots (https://repository.apache.org/snapshots): 
Transfer failed for https://repository.apache.org/snapshots/net/minidev/json-smart/2.3-SNAPSHOT/json-smart-2.3-SNAPSHOT.pom 503 Service Unavailable -> [Help 1]