Add L10N storage for localized database object content

[BurntimeX]

Summary

Introduces a dedicated L10N storage system for localized content of database objects, replacing the previous approach of storing such content as i18n phrases in wcf1_language_item. Localized values now live in a per-object <table>_l10n table (objectID, nullable languageID, payload columns), read/written through a single L10nStorage service. Captcha questions and user options are migrated to the new system as the first adopters.

The L10N system

• L10nStorage – the only writer/reader for *_l10n tables. Exchanges values as columnName => [languageID => value], supports monolingual content (languageID IS NULL, exposed as L10nStorage::MONOLINGUAL), per-column language sets, a deterministic fallback resolver (resolveValue()), and a correlated getSubSelect() for sortable/filterable list queries.
• L10nDefinition – describes a localized table (primary table, *_l10n table, object column, payload columns). Optionally declares support for synchronization with language variables via an identifierColumnName + per-column language-variable suffixes.
• Form field – IL10nFormField / TL10nFormField add ->l10n() support to form builder fields, mutually exclusive with the phrase-based ->i18n() mode.
• Collections – TCollectionL10n trait batch-loads the localized values of all objects in a DatabaseObjectCollection in a single query; OptionCollection / UserOptionCollection / CaptchaQuestionCollection and the L10n*List classes wire this into lists and grid views. L10nTextFilter filters grid columns on localized values.

Synchronization with language variables

Delivered objects (e.g. shipped user options) keep their wcf.* phrases as the source
of truth and mirror them into the L10N storage:

• The primary table gains an l10nIdentifier column (the language-variable base name, NULL for admin-created objects), and the *_l10n table an isPristine flag.
• Definitions that support the sync register via the L10nDefinitionCollecting event; SyncL10nLanguageItems runs at the end of every install/update and refreshes pristine rows from the phrases, preserving values an administrator changed locally.
• isPristine is maintained automatically inside L10nStorage::setValues(): a delivered object keeps the flag per language while the value is unchanged; a changed value or a user-created object is written as modified. L10nLanguageItemSync provides reusable one-time migrate() / ongoing sync() helpers (usable by other packages).

Migrations

• Captcha questions and user options are refactored to DatabaseObjectBuilder with dedicated create/update commands and events.
• User options move their title/description from wcf.user.option.* phrases into wcf1_user_option_l10n; system options stay linked (pristine, kept in sync), admin-created options own their values and their obsolete phrases are removed.
• UserOptionPackageInstallationPlugin and UserOptionImporter write through the new builder / L10N storage; the ACP forms, grid views, cache builder and templates read localized titles/descriptions from the collection.
• Removed template scripting from the shipped user-option descriptions, which is no longer supported for L10N content.

Notes

• New *_l10n tables are created via explicit database scripts (install + update); no automatic table provisioning.
• PackageInstallationDispatcher invokes the sync after the bootstrap loader is rebuilt, so listeners added by the same update are already active.

See #6109
See #6290