This change cleans up a few things in QueryParseContext and QueryShardContext
that make it hard to reason about the state of these context objects and are
thus error prone and should be simplified.
Currently the parser that used in QueryParseContext can be set and reset any
time from the outside, which makes reasoning about it hard. This change makes
the parser a mandatory constructor argument removes ability to later set a
different ParseFieldMatcher. If none is provided at construction time, the
one set inside the parser is used. If a ParseFieldMatcher is specified at
construction time, it is implicitely set on the parser that is beeing used.
The ParseFieldMatcher is only kept inside the parser.
Also currently the QueryShardContext historically holds an inner QueryParseContext
(in the super class QueryRewriteContext), that is mainly used to hold the parser
and parseFieldMatcher. For that reason, the parser can also be reset, which leads
to the same problems as above. This change removes the QueryParseContext from
QueryRewriteContext and removes the ability to reset or retrieve it from the
QueryShardContext. Instead, `QueryRewriteContext#newParseContext(parser)` can be
used to create new parse contexts with the given parser from a shard context
when needed.
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