support install external agent in Sermant

[lilai23]

What type of PR is this?

Feature

What this PR does / why we need it?

To better integrate with OpenTelemetry and make it easier for users to leverage its observability capabilities, we aim to treat OpenTelemetry as a component within Sermant. It will support both static and dynamic attachment methods.

Which issue(s) this PR fixes？

Fixes #1705

Does this PR introduce a user-facing change?

Yes. We will update user guide at sermant.io.

Checklist

• Make sure there is a GitHub_issue related with this PR before you start working on it.
• Make sure you have squashed your change to one single commit.
• GitHub Actions works fine in this PR.

[codecov]

Codecov Report

Attention: Patch coverage is 37.50000% with 90 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...java/io/sermant/core/ext/ExternalAgentManager.java	46.93%	25 Missing and 1 partial ⚠️
.../sermant/core/plugin/agent/config/AgentConfig.java	0.00%	12 Missing ⚠️
...c/main/java/io/sermant/core/AgentCoreEntrance.java	0.00%	10 Missing ⚠️
.../core/event/collector/FrameworkEventCollector.java	0.00%	8 Missing ⚠️
...n/agent/enhance/OpenTelemetryAgentInterceptor.java	0.00%	6 Missing ⚠️
...lement/service/heartbeat/HeartbeatServiceImpl.java	0.00%	5 Missing ⚠️
...ugin/agent/enhance/OpenTelemetryAgentDeclarer.java	0.00%	4 Missing ⚠️
...java/io/sermant/core/command/CommandProcessor.java	25.00%	3 Missing ⚠️
...e/command/ExternalAgentInstallCommandExecutor.java	78.57%	3 Missing ⚠️
.../sermant/core/plugin/agent/ByteEnhanceManager.java	0.00%	3 Missing ⚠️
... and 6 more

Flag	Coverage Δ	Complexity Δ
unittests	43.84% <37.50%> (-0.03%)	181.00 <0.00> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ	Complexity Δ
...src/main/java/io/sermant/core/command/Command.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
...in/java/io/sermant/core/common/CommonConstant.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...ore/event/collector/FrameworkEventDefinitions.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
...re/service/heartbeat/common/ExternalAgentInfo.java	100.00% <100.00%> (ø)	0.00 <0.00> (?)
.../service/hotplugging/entity/HotPluggingConfig.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
.../sermant/core/command/DynamicAgentArgsManager.java	20.00% <0.00%> (+20.00%)	0.00 <0.00> (ø)
...t/core/plugin/agent/collector/PluginCollector.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ermant/core/plugin/agent/BufferedAgentBuilder.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ore/service/heartbeat/common/HeartbeatMessage.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...src/main/java/io/sermant/core/utils/FileUtils.java	11.45% <0.00%> (-0.25%)	0.00 <0.00> (ø)
... and 11 more

... and 12 files with indirect coverage changes