Add --summary flag to bloop compile

[jozanek]

Closes #1367.

Summary

Adds bloop compile --summary, an opt-in flag that prints a compilation timing report at the end of a compile run. The feature is off by default so it does not affect interactive or IDE/BSP use.

Example output for a 4-module build where d was blocked by a failure in c:

================================================================================
b - 3314ms
a - 3244ms (failed)
d - blocked on c
Total module compile time: 6558ms
Wall-clock duration: 3412ms
================================================================================

Key design decisions:

• Opt-in only — per jvican's original comment on the issue; the flag lives on Commands.Compile and does not affect the Test/Run/Link paths through compileAnd.
• Dag-based, not cache-delta — the project set is built from Dag.dfs(getProjectsDag(…)) rather than ResultsCache.diffLatest, so every project in the requested compile closure is rendered on every run, including repeated failures where a Blocked result would be structurally equal to the cached one and would otherwise be dropped.
• Two totals — Total module compile time is the sum of per-module elapsed times (can exceed wall-clock under parallel/pipelined compilation); Wall-clock duration is a System.nanoTime measurement around the entire runCompile call, including the --incremental false clean step.
• Slowest-first ordering — most useful for CI bottleneck identification. Untimed (blocked/error) projects are grouped after timed lines, sorted alphabetically.

[tgodzik]

LGTM! That's a nice improvement

[tgodzik]

bloop.AutoCompleteSpec is failing again due to added flag, should be fine otherwise

[tgodzik]

LGTM!