macro: remove r5js.TemplateBindings#debugString.
macro: run template_bindings.js through the linter.
macro: move template_bindings.js under macro/.
runtime: run env_buffer.js through the linter.
runtime: narrow return type of r5js.{Branch,ProcCall}#evalAndAdvance.
runtime: inline the sole use of r5js.EnvBuffer#get and remove method.
runtime: move env_buffer.js under runtime/.
parse: run rename_helper.js through the linter.
parse: move rename_helper.js under parse/.
move output_modes.js to runtime/output_mode.js.
read: put r5js.Reader inside grammar.js.
main: clean up boot.js and make a method private.
main: clean up ipipeline.js.
main: remove r5js.LazyBoot.
main: r5js.boot should return a complete interpreter.
main: remove r5js.IPipeline#setRootEnv, replacing only use with ctor injection.
main: make r5js.Pipeline a @struct.
main: remove unneeded methods from r5js.PublicApi.