expression: remove redundant "errors.Trace()" in "expression" package

[ziyi-yan]

What problem does this PR solve?

fixes #8216

What is changed and how it works?

Replace all errors.Trace() to err (or the argument of errors.Trace() calls).

To get goword check passed, fix some comments.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to update the tidb-ansible repository
• Need to be included in the release note

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This change is 

[sre-bot]

Hi contributor, thanks for your PR.

This patch needs to be approved by someone of admins. They should reply with "/ok-to-test" to accept this PR for running test automatically.

[jackysp]

Thanks, @ziyi-yan !
/run-all-tests

[zz-jason]

LGTM
@lysu PTAL

[ngaut]

LGTM. Close #8216