feat(sdk-coin-polyx): add NominateBuilder for standalone nominate transactions (SI-686) #2826

Job	Run time
Generate head API spec	7m 39s
Generate merge base API spec	7m 46s
Check specs identical	4s
Generate vacuum reports for API spec	0s
Check breaking changes	0s
Linter Override	0s
API Spec Check	3s
	15m 32s

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