RFR: 8349670: HttpServer: sending interim responses fails after JDK-7026262

[Josiah Noel]

Following the guideline of the last comment on [JDK-8349670](https://bugs.openjdk.org/browse/JDK-8349670?focusedId=14794649&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14794649), resolves the issue where sending a 1xx status code would close the input stream, preventing the server from reading the body. 

- Adds a new flag checking if the incoming request is an upgrade request.
- When receiving an upgrade request, directly return the input/output stream
- When a 1xx status code is sent by `sendResponseHeaders`, the input/output streams will not be closed prematurely.
- sentHeaders will not be set to true when sending 1xx status codes

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Commit messages:
 - Merge branch 'openjdk:master' into JDK-8349670
 - Update InputRead1xxTest.java
 - Update InputRead1xxTest.java
 - support all 1xx
 - Create InputRead101Test.java
 - Send interim responses for 101 upgrade requests

Changes: https://git.openjdk.org/jdk/pull/27069/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27069&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349670
  Stats: 317 lines in 2 files changed: 293 ins; 0 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/27069.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27069/head:pull/27069

PR: https://git.openjdk.org/jdk/pull/27069