clarified migrate-database help

[rolfyone]

Had to change UnstableOptions to allow Xhelp in migrate-database as well.

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

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Note

Low Risk
Low risk CLI/help-only changes: adds Xhelp wiring for migrate-database and adjusts help output/strings without affecting database migration logic.

Overview
migrate-database now includes the hidden Xhelp subcommand so users can list unstable (--X*) flags for that command.

UnstableOptionsCommand is updated to also print hidden options defined directly on a command (not just mixins/arg groups), and the --Xto help text is reformatted/clarified to explicitly list supported RocksDB and LevelDB target versions.

^{Written by Cursor Bugbot for commit 62b8c82. This will update automatically on new commits. Configure here.}

[rolfyone]

below has new text for unstable options, which can now be listed by doing

teku migrate-database Xhelp

migrate-database unstable options
      --Xbatch-size=<integer>
                       MB per transaction (Default: 100)
                         Default: 100
      --Xdata-storage-mode=<STORAGE_MODE>
                       Sets the strategy for handling historical chain data.
                         (Valid values: ARCHIVE, PRUNE, MINIMAL, NOT_SET)
                         Default: ARCHIVE
      --Xto=<format>   The target database version to migrate to.
                       Rocksdb database types supported are 4, 5, 6.
                       Leveldb types supported are leveldb1, leveldb2.
                         Default: 6