Fix the issue that prevents compilation in C++11 environment

[JalanChao]

issue #1247 Commit 302786e introduced a definition std::is_standard_layout_v that is only supported starting from C++17, which now prevents the LevelDB project from compiling in a C++11 environment. This modification uses a C++11-compatible implementation, allowing compilation in a C++11 environment without changing the logic.

Replace std::is_standard_layout_v with std::is_standard_layout<T>::value to ensure compatibility with C++11 compilers. This change affects:

util/env_posix.cc
util/env_windows.cc
util/no_destructor.h

This fix is needed for projects that are still using C++11 and cannot upgrade to C++17. Although this change does not seem to have an impact on performance, some benchmark results are as follows: 1

./db_bench --benchmarks=fillseq,readrandom,readseq,readreverse,fillrandom,overwrite | cat
LevelDB:    version 1.23
Keys:       16 bytes each                             
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)
WARNING: Snappy compression is not enabled
------------------------------------------------
fillseq      :       2.119 micros/op;   52.2 MB/s
readrandom   :       1.189 micros/op; (1000000 of 1000000 found)
readseq      :       0.049 micros/op; 2278.8 MB/s     
readreverse  :       0.121 micros/op;  914.2 MB/s     
fillrandom   :       3.665 micros/op;   30.2 MB/s     
overwrite    :       4.458 micros/op;   24.8 MB/s     

2

./db_bench --benchmarks=fillsync,readwhilewriting --threads=4 | cat
LevelDB:    version 1.23
Keys:       16 bytes each                          
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)
WARNING: Snappy compression is not enabled
------------------------------------------------
fillsync     :    6672.317 micros/op;    0.1 MB/s (1000 ops)
readwhilewriting :       2.982 micros/op; (217660 of 1000000 found)

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[sihaixianyu]

Awesome, this is a common problem that a bunch of coders has encountered. This PR should be merged in master branch : )