Make it possible to treat empty JSON response as no params (#446)

* treat empty json as no params when optional

* add test with nested array brackets

* address grumbles: better tests

* Update types/src/v2/params.rs

Co-authored-by: David <[email protected]>

* introduce RpcParams::sequence_ignore_empty

* address grumbles: ignore empty json in RpcParams

* Update proc-macros/src/render_server.rs

* address grumbles: remove trim in next_inner()

* address grumbles: trim_start after params.next()

* address more grumbles

* [proc macros]: add test for empty array

* make proc macro kind of work

* add hack to make it work in proc macros

* add hack to make it work in proc macros

* [] ->

* revert cerebral palsy

* Update proc-macros/tests/ui/correct/basic.rs

* Update proc-macros/tests/ui/correct/basic.rs

* address grumbles

* improve is_option

* add test for core::option::Option

Co-authored-by: David <[email protected]>