lockfile: drop 1.0 lockfile support

[skshetry]

Related: #7093

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.32 ⚠️

Comparison is base (45c5c83) 91.60% compared to head (eadb7ac) 91.29%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9476      +/-   ##
==========================================
- Coverage   91.60%   91.29%   -0.32%     
==========================================
  Files         489      488       -1     
  Lines       38267    38179      -88     
  Branches     5489     5476      -13     
==========================================
- Hits        35056    34854     -202     
- Misses       2642     2730      +88     
- Partials      569      595      +26     

Impacted Files	Coverage Δ
dvc/dvcfile.py	96.45% <100.00%> (-0.31%)	⬇️
dvc/schema.py	100.00% <100.00%> (ø)
dvc/stage/loader.py	97.58% <100.00%> (-0.08%)	⬇️
tests/func/test_lockfile.py	100.00% <100.00%> (ø)
tests/unit/test_lockfile.py	100.00% <100.00%> (ø)

... and 37 files with indirect coverage changes

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