backporting initialization macro PRs (#1578)

* before/after initial block macros (#1550)

* adding init macros

* fix missing tick

* adding more documentation; fixing up emitter tests

* adding initial-guarding macro test

* prefixing macros with FIRRTL

* cleanup

* typo fix

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

* deprecating BackendCompilationUtilities trait for object (#1575)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>