Add contenthash() and .write to universalResolver/utils.ts

[adraffy]

• added KnownProfile.contenthash to get/setcontenthash()
• added Expected.write for use in setters
  - KnownBundle.write is multicall()

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The setters weren't necessary for UR testing, as DummyShapeshifterResolver doesn't use setters, but PublicResolver and namechain OwnedResolver both use setters.

[adraffy]

Probably better to just replace this with the version in namechain repo which supports all resolver profiles.