make MAX_VOTERS and MAX_CANDIDATES in elections-phragmen configurable. Fix: #11092 (#11908)

* make MAX_VOTERS and MAX_CANDIDATES in elections-phragmen configurable

* Configure election-phragmen in node bin configuring max candidates & voters

* Add document comment for added Config parameter

* Incorporate suggestion

* fix benchmarks

* Update frame/elections-phragmen/src/lib.rs

* Update frame/elections-phragmen/src/lib.rs

* fix wrong values

* fix typo

* docs

* more detailed docs

* fmt

* ".git/.scripts/bench-bot.sh" pallet dev pallet_elections_phragmen

Co-authored-by: Szegoo <[email protected]>
Co-authored-by: Sergej Sakac <[email protected]>
Co-authored-by: command-bot <>