commit-graph: place bloom_settings in context

commit-graph: place bloom_settings in context

Place an instance of struct bloom_settings into the struct
write_commit_graph_context. This allows simplifying the function
prototype of write_graph_chunk_bloom_data(). This will allow us
to combine the function prototypes and use function pointers to
simplify write_commit_graph_file().

By using a pointer, we can later replace the settings to match those
that exist in the current commit-graph, in case a future Git version
allows customization of these parameters.

Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>