Refactor dict

[bjosv]

To be able to use dict from Valkey I have found that following changes would be needed

• Rename dictSetHash* to dictSet* (matching API)
• Rename dictGetEntry* to dictGet* (matching API)
• Make dictEntry opaque
  This matches the dictEntry is valkey which also is opaque.
• Remove unused privdata from dict.
  Since the privdata pointer is not used in libvalkey we can remove it.
• Initiate dictType's using designated initializers (C99)
  Allows us to handle different ordering in the dictType struct.
• Duplicate dict value explicitly to avoid using valDup
  Valkeys dict type don't have valDup, i.e a function that can copy the inserted data.
  We can avoid this difference by manually copy the value.
• Update dictType signatures to match dict in Valkey.
  callbackHash returns an unsigned long int in valkey, we can use that as well.

With these changes we would be able to build libvalkey using dict from valkeys repos in its current state.

[zuiderkwast]

We'll most likely vendor it as before. We don't use git submodules now so that would be a large change to the tool chain, source releases, etc.

[zuiderkwast]

Looks like a cleanup. More lines deleted than added. That's always nice.