[ADT] Simplify StringMapIterBase (NFC) (#156392)

In open-adressing hash tables, begin() needs to advance to the first
valid element.  We don't need to do the same for any other operations
like end(), find(), and try_emplace().

The problem is that the constructor of StringMapIterBase says:

  bool NoAdvance = false

This increases the burden on the callers because most places need to
pass true for NoAdvance, defeating the benefit of the default
parameter.

This patch fixes the problem by changing the name and default to:

  bool Advance = false

and adjusting callers.  Again, begin() is the only caller that
specifies this parameter.

This patch fixes a "latent bug" where try_emplace() was requesting
advancing even on a successful insertion.  I say "latent" because the
request is a no-op on success.

0 files changed, 0 insertions, 0 deletions