MDEV-36542 Remove compile options for faking initialization

[grooverdan]

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• [x] The Jira issue number for this PR is: MDEV-36542

Description

Stated cases for use:

• bypass static analyizers (which should be able to see faults if they are there)
• old gcc bugs that where fixed ~4.7.

Remove defines:

• FORCE_INIT_OF_VARS
• LINT_INIT_STRUCT
• FORCE_INIT_OF_VARS

Define UNINIT_VAR make into a no-op for later branch removal.

mysql.cc - all paths in com_go populate buff before use.

json: Item_func_json_merge::val_str LINT_INIT(js2) unneeded as usage in report_error goto label only occurs after assignment to js2.

Item_func_json_contains_path::val_bool n_found initialized at same location.

_ma_ck_delete - org_key only valid under share->now_transactional likewise with _ma_ck_write_btree_with_log

Release Notes

nothing - non-functional change from user perspective

How can this PR be tested?

TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended. Consult the documentation on "Writing good test cases".

If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.

Basing the PR against the correct MariaDB version

• [ ] This is a new feature or a refactoring, and the PR is based against the main branch.
• [X] This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• [X] I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• [X] For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.