JSON performance improvements: (1) Add a cache for large string values

on OP_Column to avoid having to extract the string multiple times.
(2) Internal JSON caching improvements.

FossilOrigin-Name: 771fe35074b50b8d4a6583e61c53871b2445f7a58c82f3fc3bf6776e562e63af

diff --cc manifest
index 5c60fc278275f85ff058cee3e30ecd7cd9f9fb33,f0021c4b83e58c51c2b4f5170189941ae7232b23..03b960da65d02e5d4b8d23fd305621d1ad3b7f1a
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Correct\sa\srecently-introduced\sfalsehood\sin\sext/wasm/README.md\sregarding\sssh\sport\sforwarding.
- D 2023-07-28T11:52:58.874
 -C Mark\san\sunreachable\sbranch\sas\sALWAYS().
 -D 2023-07-28T11:30:07.088
++C JSON\sperformance\simprovements:\s\s(1)\sAdd\sa\scache\sfor\slarge\sstring\svalues\non\sOP_Column\sto\savoid\shaving\sto\sextract\sthe\sstring\smultiple\stimes.\n(2)\sInternal\sJSON\scaching\simprovements.
++D 2023-07-28T13:52:08.133
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -2049,8 -2044,8 +2049,9 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P bf71faa2a1d29ea762c4d2485522d6f4f8a5a7166981a92d3ba9c96ccbbe1213
- R 74b11dad85afdc2fb1c15f83a8016991
- U stephan
- Z 786f34221ec4345651338e5a3b199da2
 -P d3f458dcc379dd7648262f52579ec55ba931852065ed278367a0629228d0ed45
 -R 7d9c43b78a4f1c2315778caf36cecb44
++P 2a3f3a9cf28849c99d83c256f813405a2f47f84532e1192d67bb7aa655dd98a3 8fd06d1151c521515d9f7181575a04e451b522335135a27248052b067d4005ae
++R c22600634c62262906bbc544e7e5c805
++T +closed 8fd06d1151c521515d9f7181575a04e451b522335135a27248052b067d4005ae
+ U drh
 -Z c4502aa3c9cdb29d4cc267ca47a361d2
++Z 8d623546c0abbe473f1746e112ae16b4
  # Remove this line to create a well-formed Fossil manifest.

diff --cc manifest.uuid
index 80aa70205d6338e5cb80b5fbbec77c168ad423da,326a691f5a280f84b02a74a2cb5bedb18d0630af..8ee91ce04edff1e5641e255432b60b02c1e8b512
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- 2a3f3a9cf28849c99d83c256f813405a2f47f84532e1192d67bb7aa655dd98a3
 -8fd06d1151c521515d9f7181575a04e451b522335135a27248052b067d4005ae
++771fe35074b50b8d4a6583e61c53871b2445f7a58c82f3fc3bf6776e562e63af