feat: Print sccache version for Server stats

[borjamunozf]

Hi.

Coming from this discussion started by @Xuanwo , it's has been considered a good idea to include the version info when running the sccache --show-stats command.

I have included a basic solution, directly included & calling the env! macro to get the CARGO_PKG_VERSION.
One of the pending confirmations should be the display info of this new version field, as it has been mentioned that it should be explicit regarding it's the client version.

It's not a big thing, but hope to help a bit with this cool project besides my ongoing learning of Rust.
Sorry in advance for any mistake.

Thanks.

[codecov-commenter]

Codecov Report

Base: 30.93% // Head: 30.95% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (c377e28) compared to base (8b11e89).
Patch coverage: 60.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1580      +/-   ##
==========================================
+ Coverage   30.93%   30.95%   +0.02%     
==========================================
  Files          48       48              
  Lines       16625    16633       +8     
  Branches     7976     7982       +6     
==========================================
+ Hits         5143     5149       +6     
- Misses       6066     6070       +4     
+ Partials     5416     5414       -2     

Impacted Files	Coverage Δ
src/server.rs	31.67% <50.00%> (+0.70%)	⬆️
src/test/tests.rs	33.33% <100.00%> (-0.23%)	⬇️
src/util.rs	34.85% <0.00%> (-1.31%)	⬇️
src/compiler/c.rs	38.44% <0.00%> (-0.23%)	⬇️
src/compiler/msvc.rs	43.12% <0.00%> (-0.14%)	⬇️
src/lib.rs	10.79% <0.00%> (ø)
src/mock_command.rs	52.05% <0.00%> (ø)
src/compiler/args.rs	62.32% <0.00%> (ø)
src/compiler/rust.rs	33.79% <0.00%> (ø)
... and 3 more

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[sylvestre]

please add a test to make sure we don't regress in the future.
Probably something like:

sccache/tests/system.rs

Line 105 in 9c3f980

fn test_basic_compile(compiler: Compiler, tempdir: &Path) {

[borjamunozf]

please add a test to make sure we don't regress in the future. Probably something like:

sccache/tests/system.rs

Line 105 in 9c3f980

fn test_basic_compile(compiler: Compiler, tempdir: &Path) {

Agree. Nevertheless, I also have found this test, which could fit better & restricted to this? Add an extra assert or create a new one (perhaps too much for now & just a new static field)

sccache/src/test/tests.rs

Line 150 in 8b11e89

fn test_server_stats() {

Maybe I'm overthinking it too much...

[sylvestre]

Sure, as you wish :)

[sylvestre]

please run rustfmt on your change

[sylvestre]

Sorry for the latency, i wanted to verify that json file also contained it :) (and it does)