main: add support for stagedata-in-repodata, add gauges for staged/unstaged pkgs

[classabbyamp]

xbps 0.60 moves the stagedata internal to the repodata

needs Duncaen/go-xbps#1

[classabbyamp]

unstaged test repo:

# HELP repo_is_staged Non-zero if the repo is staged
# TYPE repo_is_staged gauge
repo_is_staged 0
# HELP repo_origin_time A Unix Timestamp updated every minute on the origin
# TYPE repo_origin_time gauge
repo_origin_time 0
# HELP repo_packages Packages present in the repo
# TYPE repo_packages gauge
repo_packages 2
# HELP repo_repodata_checksum CRC32 of the repodata
# TYPE repo_repodata_checksum gauge
repo_repodata_checksum 3.117631734e+09
# HELP repo_staged_packages Staged packages present in the repo
# TYPE repo_staged_packages gauge
repo_staged_packages 0

staged test repo:

# HELP repo_is_staged Non-zero if the repo is staged
# TYPE repo_is_staged gauge
repo_is_staged 1
# HELP repo_origin_time A Unix Timestamp updated every minute on the origin
# TYPE repo_origin_time gauge
repo_origin_time 0
# HELP repo_packages Packages present in the repo
# TYPE repo_packages gauge
repo_packages 2
# HELP repo_repodata_checksum CRC32 of the repodata
# TYPE repo_repodata_checksum gauge
repo_repodata_checksum 1.266242126e+09
# HELP repo_staged_packages Staged packages present in the repo
# TYPE repo_staged_packages gauge
repo_staged_packages 1

repo-default:

# HELP repo_is_staged Non-zero if the repo is staged
# TYPE repo_is_staged gauge
repo_is_staged 0
# HELP repo_origin_time A Unix Timestamp updated every minute on the origin
# TYPE repo_origin_time gauge
repo_origin_time 1.75008375e+09
# HELP repo_packages Packages present in the repo
# TYPE repo_packages gauge
repo_packages 14556
# HELP repo_repodata_checksum CRC32 of the repodata
# TYPE repo_repodata_checksum gauge
repo_repodata_checksum 2.921160341e+09
# HELP repo_staged_packages Staged packages present in the repo
# TYPE repo_staged_packages gauge
repo_staged_packages 0