ci: Fix job `build-layer-1-tests`

[jbencin]

Description

Remove remaining references to Debian Stretch while building Stacks L1. This also fixes failing integration tests by updating to subnet-traits-v1 and subnet-v2-0-0

Applicable issues

• fixes #278

[codecov[bot]]

Codecov Report

Merging #286 (2b4d0d9) into master (5d34657) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #286   +/-   ##
=======================================
  Coverage   93.40%   93.40%           
=======================================
  Files           6        6           
  Lines         349      349           
=======================================
  Hits          326      326           
  Misses         23       23           

Impacted Files	Coverage Δ
core-contracts/contracts/helper/simple-ft.clar	76.47% <ø> (ø)
core-contracts/contracts/helper/simple-nft.clar	73.33% <ø> (ø)
core-contracts/contracts/subnet.clar	96.53% <ø> (ø)
core-contracts/contracts/multi-miner.clar	95.45% <100.00%> (ø)