[jdk11u-dev] RFR: 8211978: Move testlibrary/jdk/testlibrary/SimpleSSLContext.java and testkeys to network testlibrary

[Amos Shi]

Backport of [JDK-8211978](https://bugs.openjdk.org/browse/JDK-8211978)

The following files need manual merge:
- `test/jdk/java/net/HttpURLConnection/SetAuthenticator/HTTPSetAuthenticatorTest.java` - `Copyright (c) year` sections cannot be auto merged
- `test/jdk/java/net/HttpURLConnection/SetAuthenticator/HTTPTest.java` - `Copyright (c) year` sections cannot be auto merged
- `test/jdk/java/net/httpclient/AbstractThrowingPushPromises.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/HttpsTunnelTest.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/InvalidSSLContextTest.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/ShortResponseBody.java` - `@library /lib/testlibrary` and `@build jdk.testlibrary.SimpleSSLContext` lines does not exist, just as [jdk](https://github.com/openjdk/jdk) repo, so we san safely ignore them 
- `test/jdk/java/net/httpclient/SmokeTest.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/SpecialHeadersTest.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/UnknownBodyLengthTest.java` - The base line number is different so cannot be auto merged; the changes are the same as original commit in jdk repo
- `test/jdk/java/net/httpclient/whitebox/java.net.http/jdk/internal/net/http/FlowTest.java` - `Copyright (c) year` sections cannot be auto merged
- `test/jdk/sun/net/www/protocol/http/RedirectOnPost.java` - Delete unused `@library /lib/testlibrary/` line

-------------

Commit messages:
 - Backport 4fe2edae5948e95f1940a64a3e9d4379e8362d8c

Changes: https://git.openjdk.org/jdk11u-dev/pull/2330/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2330&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8211978
  Stats: 875 lines in 122 files changed: 246 ins; 304 del; 325 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2330.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2330/head:pull/2330

PR: https://git.openjdk.org/jdk11u-dev/pull/2330