The IndexAndAliasesResolver resolves the indices and aliases for each
request and also handles local and remote indices. The current
implementation uses the ResolvedIndices class to hold the resolved
indices and aliases. While evaluating the indices and aliases against
the user's permissions, the final value for ResolvedIndices is
constructed. Prior to this change, this was done by creating a
ResolvedIndices for the first set of indices and for each additional
addition, a new ResolvedIndices object is created and merged with
the existing one. With a small number of indices and aliases this does
not pose a large problem; however as the number of indices/aliases
grows more list allocations and array copies are needed resulting in a
large amount of garbage and severely impacted performance.

This change introduces a builder for ResolvedIndices that appends to
mutable lists until the final value has been constructed, which will
ultimately reduce the amount of garbage generated by this code.