Dropped LFS3_KVONLY and LFS3_2BONLY modes for now

I think these are good ideas to bring back when littlefs3 is more
mature, but at the moment the number of different builds is creating too
much friction.

LFS3_KVONLY and LFS3_2BONLY in particular _add_ significant chunks of
code (lfs3_file_readget_, lfs3_file_flushset_, and various extra logic
sprinkled throughout the codebase), and the current state of testing
means I have no idea if any of it still works.

These are also low-risk for introducing any disk related changes.

So, ripping out for now to keep the current experimental development
tractable. May reintroduce in the future (probably after littlefs3 is
stabilized) if there is sufficient user interest. But doing so will
probably also need to come with actual testing in CI.

tests/test_kv.toml

@@ -827,7 +827,6 @@ code = '''
 
 # test kv files can be read as normal files
 [cases.test_kv_interop_reads]
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -930,7 +929,6 @@ code = '''
 
 # test normal files can be read a kv files
 [cases.test_kv_interop_writes]
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -983,7 +981,6 @@ code = '''
 # test kv files broadcast sync updates
 [cases.test_kv_interop_sync]
 defines.STICKYNOTES = [false, true]
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -1071,7 +1068,6 @@ code = '''
 # test kv files don't interfere with desync files
 [cases.test_kv_interop_desync]
 defines.STICKYNOTES = [false, true]
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -1163,7 +1159,6 @@ code = '''
 # test kv files work with resyncing files
 [cases.test_kv_interop_resync]
 defines.STICKYNOTES = [false, true]
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -1274,7 +1269,6 @@ defines.SIZE = 4
 defines.OPS = ['4*N', '40*N']
 defines.SEED = 'range(20)'
 fuzz = 'SEED'
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -1433,7 +1427,6 @@ defines.SIZE = 40000
 defines.OPS = ['4*N', '40*N']
 defines.SEED = 'range(20)'
 fuzz = 'SEED'
-ifndef = 'LFS3_KVONLY'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;