RFR: 8316433: net.dll should delay load winhttp.dll

[Daniel Jeliński]

WinHTTP functions are only used when an application:
- uses DefaultProxySelector to resolve proxies, and
- is run with -Djava.net.useSystemProxies=true

In all other cases, loading winhttp.dll is a waste of resources.

Verified that:
- existing tier1 and tier2 tests still pass
- the same system proxies are returned with and without this patch
- WinHTTP is not loaded unless DefaultProxySelector is used

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

Commit messages:
 - Delayload winhttp

Changes: https://git.openjdk.org/jdk/pull/15793/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15793&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316433
  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/15793.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15793/head:pull/15793

PR: https://git.openjdk.org/jdk/pull/15793