fix(chain): keep proxy chain members whose remarks contain a comma - #6438

Upstream 2dust#6438 stores the members of a proxy chain in
proxyChainProfileList instead of the comma-joined proxyChainProfiles,
and its one-time migration splits the old field on every comma. PattNG
already kept a comma or a backslash inside a name in that field,
escaped by a backslash, so upstream's split would cut such a name in
two ("US\, Dallas" became "US\" and "Dallas") and break the chain.

ProfileItem.moveLegacyProxyChain moves a chain into the list as PattNG
wrote it (proxyChainMembersOf: names whole, nothing trimmed) and clears
the old field; SettingsManager's migration uses it.
ProfileItem.proxyChainMembers reads the list, or a chain still stored
the old way, as after a backup of an older PattNG is restored. The
context builder and the chain editor go by it, and the editor saves the
list as upstream's does. The old writer proxyChainProfilesOf is gone.
Both functions that touch the deprecated field carry a function-scoped
suppression and the condition for their removal.

Test:
- CoreConfigContextBuilderTest (the old format read, moved once, read
  where not moved yet; hops found by whole names) and
  ServerProxyChainViewModelTest (the list saved and opened; a chain
  stored the old way opens with its names whole).

Checks:
- Not run: :app:compilePlaystoreDebugKotlin,
  :app:testPlaystoreDebugUnitTest and :app:assemblePlaystoreDebug;
  there is no Android SDK on this machine. The real context builder,
  ProfileItem and the chain, group and subscription editor view models
  were compiled with kotlinc 2.4.10 and their tests run: 30 of 30 and
  45 of 45 pass; with upstream's comma split in the migration, or
  without the old-format fallback, the new tests fail. All main and
  test sources were compiled with the stdlib alone for PattNG before
  the merge, upstream and this tree: no new error but the ServerUiState
  copy() one that is there already, and JUnit names in the new tests.
- Not run on a device: opening, saving and connecting a chain, and the
  migration of chains an older PattNG stored.