xds framework util

[daizhenyu]

What type of PR is this?

Feature.

What this PR does / why we need it?

xds framework util class to parse xds data：

1. CdsProtocolTransformer
2. RdsProtocolTransformer
3. LdsProtocolTransformer
4. XdsCommonUtils

Which issue(s) this PR fixes？

Fixes #1604

Does this PR introduce a user-facing change?

No

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 85.62092% with 22 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ment/service/xds/utils/RdsProtocolTransformer.java	80.45%	11 Missing and 6 partials ⚠️
...ment/service/xds/utils/LdsProtocolTransformer.java	85.00%	3 Missing ⚠️
...ment/service/xds/utils/CdsProtocolTransformer.java	95.12%	1 Missing and 1 partial ⚠️

Flag	Coverage Δ	Complexity Δ
unittests	43.26% <85.62%> (+0.47%)	182.00 <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
...nt/implement/service/xds/utils/XdsCommonUtils.java	100.00% <100.00%> (ø)	0.00 <0.00> (?)
...ment/service/xds/utils/CdsProtocolTransformer.java	95.12% <95.12%> (ø)	0.00 <0.00> (?)
...ment/service/xds/utils/LdsProtocolTransformer.java	85.00% <85.00%> (ø)	0.00 <0.00> (?)
...ment/service/xds/utils/RdsProtocolTransformer.java	80.45% <80.45%> (ø)	0.00 <0.00> (?)

... and 18 files with indirect coverage changes