Use Temurin over Zulu.

And, for EscapeVelocity and Inject-Common, bump our newest testing JDK from 15 to 25. A bump would probably have been a good idea years ago, but now it's forced by the fact that Temurin doesn't appear to provide a JDK 15, at least nowadays.

The change to JDK 25 sometimes has fallout:
- We'll want to update any branch-protection rules that require status checks, since the name of the check will change (because it contains the version number). However, I don't see any [for EscapeVelocity](https://github.com/google/escapevelocity/settings/branches) or [for Inject-Common](https://github.com/google/inject-common/settings/branches) (yay?), so there's nothing to update there. Contrast with, e.g., [Guava](https://github.com/google/guava/settings/branches).
- Similarly, we need to update our _Copybara_ config for the update to the name of the status check. Sadly, changes do not take effect until after submission (b/360096677), so I'll ultimately have to set `SKIP_COPYBARA` after manually verifying that all CI jobs passed.
- And of course different Java versions can be stricter about different things, perhaps especially now that we've enabled things like `maven-javadoc-plugin` by default (efbbd6c). Fortunately, that does not seem to be an issue here.

As for why we are switching to Temurin: We got [advice](google/guava#7492 (comment)) from @ben-manes: LTS versions of Temurin [come pre-installed](https://github.com/actions/setup-java/blob/main/docs/advanced-usage.md#Hosted-Tool-Cache).

Compare cl/711746683 for Guava.

RELNOTES=n/a
PiperOrigin-RevId: 813848322

Author: cpovirk

.github/workflows/ci.yml

@@ -31,7 +31,7 @@ jobs:
         uses: actions/setup-java@dded0888837ed1f317902acf8a20df0ad188d165
         with:
           java-version: ${{ matrix.java }}
-          distribution: 'zulu'
+          distribution: 'temurin'
           cache: 'maven'
       - name: 'Install'
         shell: bash