RFR: 8299976: Initialize static fields in Net eagerly [v2]

[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.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Rename, move and add clarification

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11948/files
  - new: https://git.openjdk.org/jdk/pull/11948/files/956a3170..9c9485f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11948&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11948&range=00-01

  Stats: 35 lines in 1 file changed: 4 ins; 4 del; 27 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