Extract common/port.h and optimize dbstats

[mapleFU]

This patch does two things:

1. Extract a common/port.h, which handles difference between platforms
2. DBStats is used heavily in kvrocks. So, we need to enhance it's performance. This patch uses fetch_add and aligned it with cacheline

[mapleFU]

Like rocksdb, an Per core array optimization can also be introduced here. Maybe I'll try it in another patch.

[mapleFU]

Another problem is that, should we change DBStats to unique_ptr<DBStats> in Storage? @git-hulk @PragmaTwice

[git-hulk]

I feel good about both of them since the lifetime of DBStats is the same as the storage.

[mapleFU]

Emm I think previously it's size is 8*8B=64B, now sizeof(DBStats) becomes 8 * 64B. Which would be a large object

[git-hulk]

LGTM, good patch.

[PragmaTwice]

I wonder why it will be changed for different GCC versions?

[mapleFU]

The code is borrow from rocksdb, seems it's a bug in gcc, we can ingoring it?
facebook/rocksdb@65996dd

[mapleFU]

Performance for sadd(On my WSL2 Ubuntu22, with gcc11.4, CPU AMD 3800X) with default release build:

before:
SADD: 27173.91 requests per second

after:
SADD: 30211.48 requests per second

cc @git-hulk @PragmaTwice

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
67.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud