resurrect ssh multiplexing

[ndeloof]

- What I did
resurrect #2132 which has been reverted due to CI flakyness

- How I did it
git revert + sme tweaks to adjust to current codebase

- How to verify it

- Description for the changelog
Add multiplexing to ssh connection helper so commands that do multiple requests share the connection. Environment variables for opting out and controlling the persist time for even better connection sharing.

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Merging #4699 (937954d) into master (cddd186) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4699      +/-   ##
==========================================
- Coverage   59.75%   59.72%   -0.04%     
==========================================
  Files         287      287              
  Lines       24821    24835      +14     
==========================================
  Hits        14832    14832              
- Misses       9103     9117      +14     
  Partials      886      886              

[thaJeztah]

Some minor linting issues; one of them is probably to use 0o700 instead of 0700 (the new format with the o for octal)

59.95 cli/connhelper/connhelper.go:10: File is not `gofumpt`-ed (gofumpt)
59.95 	"strconv"
59.95 cli/connhelper/connhelper.go:86: File is not `gofumpt`-ed (gofumpt)
59.95 	if err := os.MkdirAll(config.Dir(), 0700); err != nil {
59.95 cli/connhelper/connhelper.go:89: File is not `gofumpt`-ed (gofumpt)
59.95 	sshFlags = append(sshFlags, "-o", "ControlMaster=auto", "-o", "ControlPath=" + config.Dir() + "/%r@%h:%p")
59.95 cli/connhelper/connhelper.go:103: File is not `gofumpt`-ed (gofumpt)
59.95 
59.95 cli/connhelper/connhelper.go:102: File is not `goimports`-ed (goimports)

[thaJeztah]

Oh! And looks like you missed adding DCO sign-offs 😅