embed: resolve string, []byte issues

[rsc]

Proposals #43216 and #43217 need to be resolved before the Go 1.16 release. Filing this issue in the Go 1.16 milestone for them.

[toothrot]

@rsc Is this ok to label as okay-after-beta1, or do you feel like this should block the Go 1.16 beta?

[ianlancetaylor]

This should not block the beta.

[ianlancetaylor]

Proposals #43216 and #43217 have been resolved, so closing this issue.