CTM-628 pd-balanced boot disks are actually pretty good

[aednichols]

Take advantage of pd-balanced "baseline performance" of 3,000 IOPS + 140 MiBps [0].

Those (great) performance figures are suspiciously identical to Hyperdisk Balanced [1], the newest disk type.

Indeed, pd-balanced got this upgrade in 2022 [2] just before Hyperdisk GA [3]; perhaps it's now implemented on a shared platform with Hyperdisk.

250 GB pd-standard: 30 MiB/s, 188 IOPS read, 375 IOPS write
100 GB pd-balanced: 168 MiB/s, 3,600 IOPS read/write

[0] https://docs.cloud.google.com/compute/docs/disks/performance#baseline_performance
[1] https://docs.cloud.google.com/compute/docs/disks/hd-types/hyperdisk-balanced#default-perf
[2] https://docs.cloud.google.com/compute/docs/release-notes-archive#November_14_2022
[3] https://docs.cloud.google.com/compute/docs/release-notes-archive#March_13_2023

Testing to do: evaluate against scenarios in #3594 to make sure we have enough space for large custom images. The free space math changed significantly with #4922.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.88%. Comparing base (9a4374d) to head (0b8bf38).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4925      +/-   ##
===========================================
+ Coverage    73.87%   73.88%   +0.01%     
===========================================
  Files          131      131              
  Lines        11207    11208       +1     
  Branches       957      949       -8     
===========================================
+ Hits          8279     8281       +2     
+ Misses        2928     2927       -1     

Files with missing lines	Coverage Δ
...titute/dsde/workbench/leonardo/config/Config.scala	97.97% <100.00%> (+0.17%)	⬆️
.../dsde/workbench/leonardo/util/GceInterpreter.scala	66.83% <ø> (ø)

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