feat: add fixed_ip parameter and response function of rename

[Lance52259]

What this PR does / why we need it:

1. Rds instance need support fixed_ip for code refactor.
2. Error return of rename function isn't compliance with design specifications.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged):
reference: #383

Special notes for your reviewer:

Release note:

1. new fixed_ip parameter.
2. new RenameResult struct and extract.
3. update error return of rename function form golangsdk.Result to RenameResult.

[coveralls]

Pull Request Test Coverage Report for Build 1204

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 68.171%

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Totals
Change from base Build 1203:	0.0%
Covered Lines:	11559
Relevant Lines:	16956

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💛 - Coveralls