Format JVM metrics units for Tomcat

[Paamicky]

Description of the issue

Since CWA v1.300061.0, the bundled JMX Metric Gatherer JAR switched Tomcat/JVM metric units to UCUM annotation format ({session}, {thread}, {class}, {collection}, {request}, {error}). The agent's knownNonConvertibleUnits set only contains old-format strings, causing non-convertible unit warning logs every collection interval. No data loss occurs (metrics still publish with unit None), but the log noise degrades readability for customers running Tomcat/JVM monitoring.

Issue: https://issues.amazon.com/issues/CWQS-3574

Description of changes

• Added the six UCUM annotation units ({session}, {error}, {thread}, {request}, {class}, {collection}) to the knownNonConvertibleUnits set in internal/cloudwatch/unit.go. This suppresses the spurious warning logs without changing metric publishing behavior.

License

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Tests

• Added unit test cases for all six new UCUM annotation units in TestKnownNonStandardUnits
• Verified ToStandardUnit returns no error and maps them to None with scale 0

Requirements

1. Run make fmt and make fmt-sh
2. Run make lint

Integration Tests

To run integration tests against this PR, add the ready for testing label.

[github-actions]

Binary Size Report

linux/amd64

Binary	PR	vs main (5efb6c4)	vs v1.300070.0
amazon-cloudwatch-agent	193.3 MB	+0 B	${\color{green}▼}$ 38.0 MB (-16.4%)
amazon-cloudwatch-agent-config-wizard	2.0 MB	+0 B	${\color{red}▲}$ +86.0 KB (+4.5%)
config-downloader	2.0 MB	+0 B	${\color{red}▲}$ +86.0 KB (+4.5%)
config-translator	2.0 MB	+0 B	${\color{red}▲}$ +86.0 KB (+4.5%)
start-amazon-cloudwatch-agent	2.5 MB	+0 B	${\color{red}▲}$ +81.9 KB (+3.4%)
workload-discovery	3.0 MB	+0 B	${\color{red}▲}$ +94.2 KB (+3.2%)
Total	204.8 MB	+0 B	${\color{green}▼}$ 37.6 MB (-15.5%)

linux/amd64 amazon-cloudwatch-agent (last 9 main commits + this PR)

 193 ┤                                        
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 193 ┤▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ███ ███ ███ 
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      43f2526                             PR

linux/arm64

Binary	PR	vs main (5efb6c4)	vs v1.300070.0
amazon-cloudwatch-agent	177.1 MB	+0 B	${\color{green}▼}$ 34.4 MB (-16.3%)
amazon-cloudwatch-agent-config-wizard	2.0 MB	+0 B	${\color{green}▼}$ 22 B (-0.0%)
config-downloader	2.0 MB	+0 B	${\color{green}▼}$ 22 B (-0.0%)
config-translator	2.0 MB	+0 B	${\color{green}▼}$ 22 B (-0.0%)
start-amazon-cloudwatch-agent	2.4 MB	+0 B	${\color{red}▲}$ +65.5 KB (+2.8%)
workload-discovery	2.9 MB	+0 B	${\color{red}▲}$ +65.5 KB (+2.3%)
Total	188.4 MB	+0 B	${\color{green}▼}$ 34.3 MB (-15.4%)

windows/amd64

Binary	PR	vs main (5efb6c4)	vs v1.300070.0
amazon-cloudwatch-agent.exe	196.1 MB	${\color{red}▲}$ +6.1 KB (+0.0%)	${\color{green}▼}$ 38.1 MB (-16.3%)
amazon-cloudwatch-agent-config-wizard.exe	2.1 MB	+0 B	${\color{red}▲}$ +130.6 KB (+6.5%)
config-downloader.exe	2.1 MB	+0 B	${\color{red}▲}$ +130.0 KB (+6.5%)
config-translator.exe	2.1 MB	+0 B	${\color{red}▲}$ +130.6 KB (+6.5%)
start-amazon-cloudwatch-agent.exe	2.3 MB	+0 B	${\color{red}▲}$ +112.1 KB (+5.2%)
workload-discovery.exe	2.9 MB	+0 B	${\color{red}▲}$ +97.3 KB (+3.5%)
Total	207.7 MB	${\color{red}▲}$ +6.1 KB (+0.0%)	${\color{green}▼}$ 37.5 MB (-15.3%)

Investigating size changes

Use go-size-analyzer to compare binaries:

GOEXPERIMENT=jsonv2 go install github.com/Zxilly/go-size-analyzer/cmd/gsa@latest
gsa diff --old <baseline-binary> --new <new-binary>