feat(sdk-coin-polyx): add NominateBuilder for standalone nominate transactions (SI-686) #2827

Job	Run time
Generate merge base API spec	8m 43s
Generate head API spec	8m 6s
Check specs identical	3s
Check breaking changes	0s
API Spec Check	2s
Generate vacuum reports for API spec	0s
Linter Override	0s
	16m 54s

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