[flutter_tool] Report rss high watermark in command analytics events

[zanderso]

Description

This PR adds memory high watermark information in command completion events. This is a step toward determining whether long-running tool commands have high memory usage.

Related Issues

Reports from twitter

Tests

I added the following tests:

Added a test to flutter_command_test.dart.

Breaking Change

Does your PR require Flutter developers to manually update their apps to accommodate your change?

• Yes, this is a breaking change (Please read [Handling breaking changes]). Replace this with a link to the e-mail where you asked for input on this proposed change.
• No, this is not a breaking change.

[codecov]

Codecov Report

Merging #40988 into master will decrease coverage by 0.81%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master   #40988      +/-   ##
==========================================
- Coverage   60.58%   59.77%   -0.82%     
==========================================
  Files         192      192              
  Lines       18649    18663      +14     
==========================================
- Hits        11299    11155     -144     
- Misses       7350     7508     +158

Flag	Coverage Δ
#flutter_tool	59.77% <85.71%> (-0.82%)	⬇️

Impacted Files	Coverage Δ
...ckages/flutter_tools/lib/src/reporting/events.dart	96.82% <100%> (+0.27%)	⬆️
...ackages/flutter_tools/lib/src/reporting/usage.dart	85.33% <100%> (-3.93%)	⬇️
packages/flutter_tools/lib/src/context_runner.dart	71.42% <100%> (+0.51%)	⬆️
packages/flutter_tools/lib/src/base/io.dart	53.33% <71.42%> (+3.33%)	⬆️
packages/flutter_tools/lib/src/ios/devices.dart	36.28% <0%> (-29.12%)	⬇️
...s/flutter_tools/lib/src/windows/visual_studio.dart	73.52% <0%> (-20.59%)	⬇️
...ages/flutter_tools/lib/src/protocol_discovery.dart	86.2% <0%> (-10.35%)	⬇️
packages/flutter_tools/lib/src/convert.dart	58.33% <0%> (-8.34%)	⬇️
packages/flutter_tools/lib/src/asset.dart	78.9% <0%> (-6.76%)	⬇️
... and 9 more

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[blasten]

LGTM!