refactor(layers/prometheus): provide builder APIs #1649

Job	Run time
build_all_features	4m 44s
build_all_platforms (ubuntu-latest)	2m 33s
check_clippy	3m 32s
build_default_features (ubuntu-latest)	1m 0s
build_all_platforms (macos-latest)	2m 28s
build_default_features (macos-latest)	35s
build_all_platforms (windows-latest)	6m 36s
check_docs	3m 4s
build_default_features (windows-latest)	2m 22s
unit	6m 26s
check_msrv	33s
build_under_wasm	46s
	34m 39s

Provide feedback