[Refactor] XContentFactory contentType introspection to MediaTypeRegistry

[nknize]

XContentFactory is tightly coupled to concrete XContentType. This PR builds on the MediaType abstractions, specifically MediaTypeRegistry, to decouple contentType( introspection (e.g., determining type from byte streams) from concrete XContentType implementations. This removes the tight coupling of :libs:opensearch-x-content with abstract interface contracts currently defined in :server further enabling the ability to refactor those contracts from :server to the proper library for modularity and extensibility.

relates #5910
relates #8110

depends on #8636

[nknize]

Reminder: this PR is larger than it's actual change because it includes (depends on) #8636

[nknize]

I ran across a flaky test w/ RemoteFSTranslogTests when running :server:test locally. It does not repro on it's own (hence "flaky") so I could not chase the failure.

./gradlew ':server:test' --tests "org.opensearch.index.translog.RemoteFSTranslogTests.testConcurrentWriteViewsAndSnapshot" -Dtests.seed=11209ED8456F2E6A -Dtests.security.manager=true -Dtests.jvm.argline="-XX:TieredStopAtLevel=1 -XX:ReservedCodeCacheSize=64m" -Dtests.locale=sr-ME -Dtests.timezone=Pacific/Johnston -Druntime.java=20

I documented this on #5823 for posterity.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/20702/
• CommitID: f2da36a
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/21280/
• CommitID: bdecf35
  Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green.
  Is the failure a flaky test unrelated to your change?

[nknize]

@reta this one will be ready to go as well

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/21300/
• CommitID: 4899c0d

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-8826-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 36c37ace30cdf9d2f92176a3aa38b60865c33056
# Push it to GitHub
git push --set-upstream origin backport/backport-8826-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-8826-to-2.x.

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-8826-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 36c37ace30cdf9d2f92176a3aa38b60865c33056
# Push it to GitHub
git push --set-upstream origin backport/backport-8826-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-8826-to-2.x.