Deprecate obsolete disable-precheck flag

Context

Remove the obsolete disable_mempool parameter from shell_limits (it is unused since V16.0~rc1), and deprecate the corresponding disable-mempool node configuration flag.

Fixes an item of #5279 (closed).

Follow-up issue: #5767 (closed)

Manually testing the MR

Mostly CI

May also run a node with the flag set to true or false, either from the command line or from the config file. Check that it doesn't fail and the node's behavior is unaffected either way.

Checklist

• n/a Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• n/a (no semantic changes) Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR