This commit implements safe navigation for CallNodes,
CallAndWriteNodes and CallOperatorWriteNodes

* Start using the renamed `PM_KEYWORD_HASH_NODE_FLAGS_SYMBOL_KEYS` flag
to check if all keys of the keyword hash node are symbols.
* For arguments passed as a hash, start marking them as `KW_SPLAT_MUT` only if the number of entries in the hash is greater than 1 (which is what the old compiler used to do).

This commit adjusts the local table size to be consistent regardless
of the number of anonymous locals.

This PR fixes two bugs when compiling optional keyword parameters:
- It moves keyword parameter compilation to STEP 5 in the parameters
sequence, where the rest of compilation happens. This is important
because keyword parameter compilation relies on the value of
body->param.keyword->bits_start which gets set in an earlier step
- It compiles array and hash values for keyword parameters, which
it didn't previously