Add FirtoolBinaryPath option (#3434)

* Add FirtoolBinaryPath option

* Format

* Add Scaladoc

* Add HasShellOptions

* Fix build

* Update src/main/scala/circt/stage/Annotations.scala

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>

* Register shell option

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Co-authored-by: Schuyler Eldridge <schuyler.eldridge@gmail.com>