Migrate to new coverage build introduced from go1.20

[wuhuizuo]

We only need go build -cover to build the binary for integration testing, It will be simpler for building and testing.

Branch: master, release-7.1

Ref:

• https://github.com/pingcap/tidb/blob/c4756df3b4e6ba6b5a532e0999ac3a28c40fa31a/Makefile#L203C1-L208
• https://go.dev/blog/integration-test-coverage

[bb7133]

Please notice that the TiDB server from go build -cover is able to get the coverage result only when it is shut down gracefully.