Replace mock time implementation

[gammazero]

The package github.com/benbjohnson/clock is archived, i.e. no longer maintained, and should be replaced with a fork that is maintained. The github.com/filecoin-project/go-clock is such a fork and has fixes to existing issues in the original package.

Closes #753

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.34%. Comparing base (6151dae) to head (d909bfe).
Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #762      +/-   ##
==========================================
- Coverage   60.45%   60.34%   -0.12%     
==========================================
  Files         245      245              
  Lines       31101    31101              
==========================================
- Hits        18803    18768      -35     
- Misses      10629    10659      +30     
- Partials     1669     1674       +5     

Files with missing lines	Coverage Δ
...client/internal/messagequeue/donthavetimeoutmgr.go	93.98% <ø> (ø)
...tswap/client/internal/messagequeue/messagequeue.go	84.54% <ø> (-0.77%)	⬇️
bitswap/server/internal/decision/scoreledger.go	94.11% <ø> (ø)
routing/http/client/client.go	70.83% <ø> (ø)

... and 12 files with indirect coverage changes