RFR: 8375350: Remove usage of AppContext from javax.imageio implementation [v2]

[Phil Race]

> Remove usage of AppContext from Image IO

Phil Race has updated the pull request incrementally with one additional commit since the last revision:

  8375350

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29236/files
  - new: https://git.openjdk.org/jdk/pull/29236/files/d8814466..37d255b3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29236&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29236&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29236.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29236/head:pull/29236

PR: https://git.openjdk.org/jdk/pull/29236