Merge bitcoin/bitcoin#22653: refactor: Rename JoinErrors and re-use it

bb56486a17 refactor: Reuse MakeUnorderedList where possible (Hennadii Stepanov)
77a90f03ac refactor: Move MakeUnorderedList into util/string.h to make it reusable (Hennadii Stepanov)
6a5ccd65c7 scripted-diff: Rename JoinErrors in more general MakeUnorderedList (Hennadii Stepanov)

Pull request description:

  A nice `JoinErrors` utility function was introduced in https://github.com/bitcoin-core/gui/pull/379 by Russell Yanofsky.

  This PR renames this function and re-uses it across the code base.

ACKs for top commit:
  Zero-1729:
    Concept ACK bb56486a17
  theStack:
    Code-review ACK bb56486a17
  Talkless:
    utACK bb56486a17
  ryanofsky:
    Code review ACK bb56486a17. Nice deduping, thanks for this!

Tree-SHA512: 6bdbfa61f2ffa69e075f46b733f247c6d5b8486779a1dac064285a199a4bb8bc5ef44eaee37086305646b5c88eb6a11990883219a4a9140a5117ee21ed529bb9

src/rpc/blockchain.cpp

@@ -36,6 +36,7 @@
 #include <txmempool.h>
 #include <undo.h>
 #include <util/strencodings.h>
+#include <util/string.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <validation.h>
@@ -1328,7 +1329,7 @@ static RPCHelpMan verifychain()
                 "\nVerifies blockchain database.\n",
                 {
                     {"checklevel", RPCArg::Type::NUM, RPCArg::DefaultHint{strprintf("%d, range=0-4", DEFAULT_CHECKLEVEL)},
-                        strprintf("How thorough the block verification is:\n - %s", Join(CHECKLEVEL_DOC, "\n- "))},
+                        strprintf("How thorough the block verification is:\n%s", MakeUnorderedList(CHECKLEVEL_DOC))},
                     {"nblocks", RPCArg::Type::NUM, RPCArg::DefaultHint{strprintf("%d, 0=all", DEFAULT_CHECKBLOCKS)}, "The number of blocks to check."},
                 },
                 RPCResult{