[LLDB][ExpressionParser] Fix indices inside format-strings passed to LLDB_LOG

llvm::formatv expects the parameter indexes to start with 0.
Unfortunately it doesn't detect out-of-bounds accesses in the format
string at compile-time, of which we had several inside ClangExpressionDeclMap.

This patch fixes these out-of-bounds format accesses.

Example output

Before

ClangExpressionDeclMap::FindExternalVisibleDecls for '$__lldb_class' in a
'TranslationUnit'
  CEDM::FEVD Searching the root namespace
  CEDM::FEVD Adding type for $__lldb_class: 1

After

ClangExpressionDeclMap::FindExternalVisibleDecls for '$__lldb_class' in
a 'TranslationUnit'
  CEDM::FEVD Searching the root namespace
  CEDM::FEVD Adding type for $__lldb_class: class (lambda)

Patch by Michael Buch!

Differential Revision: https://reviews.llvm.org/D128063