server: refactor session and sessiontxn

[cfzjywxk]

What problem does this PR solve?

Issue Number: ref #41098

Problem Summary:

Refactor and unify the session and transaction interfaces and usages.

What is changed and how it works?

1. Move the LazyTxn struct from session to txnManager. LazyTxn is a wrapper to use KV.Transaction utilities for session, it should be refactored and merged into txnManager in the future, so the session has a unified entry the TxnManager interface to communicate with the transaction engine or module.
2. Unify the OnStmtStart and OnStmtEnd from txnManager and LazyTxn into one.
3. Record the Valid state in TxnInfo for the session manager.
4. Move the lock-view related Txninfo from the session package to the sessiontxn package.

Check List

Tests

• Unit test

Side effects

Documentation

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

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[cfzjywxk]

/retest-required

[cfzjywxk]

/retest

[ti-chi-bot]

@cfzjywxk: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	ee8c74c86b986b0d982bd020da12a36114b537fe	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev_2	953eb41	link	true	/test check-dev2

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