Enhance the EXPLAIN QUERY PLAN output to use symbolic names to describe

subqueries, where possible, instead of cryptic subquery index numbers.
And in other ways, make the EQP output cleaner and easier to read.  Little
code is changed, but many of the test results had to be tweaked to align
with the new output format.

FossilOrigin-Name: f8e28308fdb45fbdef30003320d653410d69bb8ec92eef35c4245a99e2d0603b

diff --cc manifest
index ecd013448c5833b63a3d20853a10e8bdf48a9399,ce505cdd02e363438ea1bb27870fdd417a42a8ad..7c280e82c52fee284b472c3329f790096e61beb0
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--- 2/manifest
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@@@ -1,5 -1,5 +1,5 @@@
- C Increase\sthe\sversion\snumber\sto\s3.36.0\sto\sbegin\sthe\snext\sdevelopment\scycle.
- D 2021-03-22T16:50:39.437
 -C Merge\srecent\sfixes\sfrom\strunk.
 -D 2021-03-22T18:53:26.486
++C Enhance\sthe\sEXPLAIN\sQUERY\sPLAN\soutput\sto\suse\ssymbolic\snames\sto\sdescribe\nsubqueries,\swhere\spossible,\sinstead\sof\scryptic\ssubquery\sindex\snumbers.\nAnd\sin\sother\sways,\smake\sthe\sEQP\soutput\scleaner\sand\seasier\sto\sread.\s\sLittle\ncode\sis\schanged,\sbut\smany\sof\sthe\stest\sresults\shad\sto\sbe\stweaked\sto\salign\nwith\sthe\snew\soutput\sformat.
++D 2021-03-23T01:06:02.016
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