WL#8066: True bottom-up server parser: refactoring of the HANDLER statement

Affects: Server-8.0   —   Status: Complete   —   Priority: Medium

This WL is intended to refactor HANDLER statement-related parser
grammar rules in a pure bottom-up style to make it (grammar) context-independent
for the better maintainability and extendibility.
Functional requirements
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N/A

Non-functional requirements
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NF-1: No performance degradation is expected.
Goals
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This WL is intended to refactor the grammar of the `HANDLER` statement in a pure context-independent bottom-up style for the better maintainability and extendibility.

This WL uses the framework and the methodology of the refactoring from the WL#7199 "True bottom-up server parser: common framework for the refactoring".

User Documentation
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No user-visible changes. No documentation required. 
New parse tree node classes
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Class name                  | Related syntax
----------------------------|------------------
PT_handler_open             | `HANDLER [<db>.]<table> OPEN [<alias>]`
PT_handler_close            | `HANDLER <name> CLOSE`
PT_handler_table_scan       | `HANDLER <name> READ FIRST/NEXT [WHERE <expr>] [LIMIT <expr>]`
PT_handler_index_scan       | `HANDLER <name> READ <index> FIRST/NEXT/PREV/LAST [WHERE <expr>] [LIMIT <expr>]`
PT_handler_index_range_scan | `HANDLER <name> READ <index> EQ/GE/LE/GT/LT '(' <expr> [,...] ')' [WHERE <expr>] [LIMIT <expr>]`


Removal of unneeded "global" variables
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* Yacc_state::m_ha_rkey_mode
* LEX::handler_insert_list