assert: deprecate CompareType

[dolmen]

Summary

Mark assert.CompareType as deprecated.

Changes

Commits step by step:

• Refactor tests to free the compareResult symbol name: d75ed1dbce63d7f994be0afb3eabe1886c722844, 539cfd9c2763e2dab63926ed9fc435e478346f2b
• Rename CompareType to compareResult: fc30ce69c521b8b47adaf4f812bde58bc677767a
• Reinstate CompareType but mark it as deprecated: 05f46a65dc8c220d160a5dac12d81fe97b51c0be

Motivation

assert.CompareType has been introduced by 0b4ff03cda5c8eb0150a14ffbaaa088fd777d6ba and published since v1.6.0, but it is in fact only for internal usage and should never have been exposed.

A search of usage of assert.CompareType on GitHub shows no results: https://github.com/search?q=assert.CompareType%20language%3AGo%20&type=repositories

Related issues

N/A

[dolmen]

Similar PR about deprecating a private type that should not have been exposed: #1441.