v3 migration

[shirou]

Thanks @Lomanic , PR count gradually becomes lower and golang mod becomes enables by default, I am thinking about migration to v3 (finally, sorry)

This PR includes migration scripts from current v2 to v3. to use this script, bash tools/v3migration/v3migration.sh with go build environment.

issues

All issues should be also filed in #362.

• RlimitStat change to int64 from uint64 (add current values to rlimit retrieval #346)
• remove process.NetIoCounter() (process.NetIOCounters is pointless on Linux #429)
• fix typo: "memoryLimitInBbytes" -> memoryLimitInBytes (CgroupMem : fix typo and wrong file names #464)
• add WithContext methods ([Windows] cpu.Info() timing out #469)
• process.GetWin32Proc should not be exposed
• mem.VirtualMemoryStat JSON fields proper capitalization (mem.VirtualMemoryStat JSON fields capitalization and TestX_String tests #545)
• more broadly, have the same public API/types on all platforms (no more public API/types/constants defined only for some platforms)
• return detailed state in process.State (as []string, err), instead of just one state (currently, R: Running S: Sleep T: Stop I: Idle Z: Zombie W: Wait and L: Lock). Linked to Determine if process is running in the foreground #596 (determining background state, see Determine if process is running in the foreground #596 (comment))
• get docker container cpu usage from cpuacct.usage (get docker container cpu usage from cpuacct.usage #590 and get docker container cpu usage from cpuacct.usage #581)
• disk.Opts should be string[] not string. (related to [disk][linux] flag bind mounts #955)
• Fixed temperature sensors detection in Linux (Fixed temperature sensors detection in Linux #905)
• disk.GetDiskSerialNumber is only for linux. Rename SerialNumber, change return type to (string, error), and returns NotImplementError for other platforms
• disk.GetLabel is only for linux. Rename to Label, change return type to (string, error), and returns NotImplementError for other platforms and
• Change net.InterfaceStat.Addrs to InterfaceAddrList Return a valid JSON String() output for network lists #226

schedule

• ～ 2020-09-30:Collect issues with breaking changes. implement migration script. adding v3 to this PR is not permitted. so we can merge PR into current v2 if no breaking change.
• 2020-09-30: Add v3 directory to this PR
• ～ 2020-10-31: Start to implement complex change by hand.
• 2020-10-31: Release v3.20.10

[shirou]

• disk.Opts should be string[] not string. (related to [disk][linux] flag bind mounts #955)

[Lomanic]

Maybe this PR should target a new v3 branch, this way we could be iterating in this branch in smaller steps. What do you think @shirou?

[shirou]

Thank you foe the comment. I think v3 directory in master branch is better to follow go module manner. so this PR targets master branch.

and after merge this PR, we can still develop v2 because different directory.

[shirou]

• merge Fixed temperature sensors detection in Linux #905 to v3.