Mark various unreachable branches in rtree.c with ALWAYS() or NEVER().

FossilOrigin-Name: 4fab9089868bbb05a192da09bc201f0a84c5b9bef39dcb063afc1d7658299fdd

diff --cc manifest
index 6454e97831b594721bbf3ec45c28611a54a60b36,e29199bb7562876bfc50a1316ac1f65690396d9a..f303ec17eb2aea3d987277908ff0a56ea4c25d63
--- 1/manifest
--- 2/manifest
+++ b/manifest
@@@ -1,5 -1,5 +1,5 @@@
- C Fix\sthe\sxBestIndex\smethod\son\srtree\sso\sthat\sit\scorrectly\srecognizes\sthat\nrowid=?\sworks\sthe\ssame\sas\sid=?.
- D 2021-09-15T16:20:15.282
 -C New\sALWAYS()\sand\sassert()\sto\smark\sunreachable\sbranches\sin\srtree.c.
 -D 2021-09-16T05:24:40.469
++C Mark\svarious\sunreachable\sbranches\sin\srtree.c\swith\sALWAYS()\sor\sNEVER().
++D 2021-09-16T05:39:07.773
  F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
  F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
  F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@@ -1923,7 -1923,7 +1923,8 @@@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a9
  F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
  F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
  F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
- P 9123f680ae3100f4c781ac4f5b8afac49bb5d4231b5931ad112b1b615f22f613
- R aa32b780c45fbdfaa5c4a0c43e497966
 -P cbaac8878aac0623beb5af3bc79a5b1c0179213206fd658b8c4fcc3531889480
++P c74c07cc86443057d34284ae31eb68470741592b0e61072fd5e120e82919169b f7ad73c49507c9436adc7fe1b865f801eefcc7ea6b3ba35e83e63029beb03016
+ R 37a433ae96b1c5a938d63509ab7d490e
++T +closed f7ad73c49507c9436adc7fe1b865f801eefcc7ea6b3ba35e83e63029beb03016
  U drh
- Z 5cf9ad391dbbe3a117e87c8cd398587f
 -Z d12f96c6d48b6f5bf9c6c89486ebfbc1
++Z 72919531593fe5f120dc25a5a4b2d7d0

diff --cc manifest.uuid
index e3c694974db68aaa6a7aba2dbfdb4b7f2af689e8,3251ebd0083096fef987eb2da1fa3b3428568f01..9299df9e263186e247bbe4e4aa4dd72bdaaed664
--- 1/manifest.uuid
--- 2/manifest.uuid
+++ b/manifest.uuid
@@@ -1,1 -1,1 +1,1 @@@
- c74c07cc86443057d34284ae31eb68470741592b0e61072fd5e120e82919169b
 -f7ad73c49507c9436adc7fe1b865f801eefcc7ea6b3ba35e83e63029beb03016
++4fab9089868bbb05a192da09bc201f0a84c5b9bef39dcb063afc1d7658299fdd