Drop support for contact-less sessions

[rowanseymour]

Not convinced it ever worked and we have no plans to ever utilize this functionality

Also drops long deprecated connection field on IVR triggers which was replaced by call

[codecov]

Codecov Report

Merging #1192 (c35e2a2) into main (e3856f2) will decrease coverage by 0.05%.
The diff coverage is 20.00%.

@@            Coverage Diff             @@
##             main    #1192      +/-   ##
==========================================
- Coverage   87.71%   87.66%   -0.05%     
==========================================
  Files         262      262              
  Lines       11002    10961      -41     
==========================================
- Hits         9650     9609      -41     
  Misses        929      929              
  Partials      423      423              

Files	Coverage Δ
flows/actions/add_contact_groups.go	100.00% <ø> (ø)
flows/actions/add_contact_urn.go	100.00% <ø> (ø)
flows/actions/remove_contact_groups.go	100.00% <ø> (ø)
flows/actions/send_msg.go	90.00% <ø> (-0.70%)	⬇️
flows/actions/set_contact_channel.go	100.00% <ø> (ø)
flows/actions/set_contact_field.go	100.00% <ø> (ø)
flows/actions/set_contact_language.go	100.00% <ø> (ø)
flows/actions/set_contact_name.go	100.00% <ø> (ø)
flows/actions/set_contact_status.go	100.00% <ø> (ø)
flows/actions/set_contact_timezone.go	100.00% <ø> (ø)
... and 3 more

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