RFR: 8299976: Initialize static fields in Net eagerly

[Per Minborg]

This PR proposes initializing some static fields eagerly using `final` fields. 

This will improve performance slightly and will allow us to remove two static fields.

The PR also contains "blessed" variable casing and deduplication of exception creation.

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Commit messages:
 - Update copyright year
 - Revert MC access
 - Use MH and deduplicate exeption constuction
 - Rollback changes
 - Initialize Net eagerly, improve in accessors and cleanup

Changes: https://git.openjdk.org/jdk/pull/11948/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11948&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299976
  Stats: 98 lines in 1 file changed: 13 ins; 15 del; 70 mod
  Patch: https://git.openjdk.org/jdk/pull/11948.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11948/head:pull/11948

PR: https://git.openjdk.org/jdk/pull/11948