RFR: 8286873: Improve websocket test execution time

[Daniel Jeliński]

This PR improves the execution time of jdk_net tests (and, by extension, tier2) by about 3 minutes.

Tests located under `jdk/java/net/httpclient/websocket` are never run in parallel. Each of the 8 modified `Pending***` tests originally required 40 seconds to complete. After the proposed changes, they usually complete in 15 seconds.

This PR modifies the tests to initially run with 1 second timeout. If the test fails with 1 second timeout, it is retried with timeout increased to 10 seconds (the original value).

The modified tests were executed at least 10 times on each of: Windows, Linux (both x64 and aarch64), MacOS (both x64 and aarch64). No failures were observed.

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Commit messages:
 - Explain magic timeouts
 - Retry all operations
 - Increase initial wait for Windows machines
 - Fix test retry
 - Avoid one 5-second wait
 - Use shorter timeout on the first try

Changes: https://git.openjdk.java.net/jdk/pull/8746/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8746&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286873
  Stats: 139 lines in 10 files changed: 70 ins; 38 del; 31 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8746.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8746/head:pull/8746

PR: https://git.openjdk.java.net/jdk/pull/8746