Drop MSRV to 1.65 and bump toml, mock_instant

[Dirreke]

As toml has drop their MSRV to 1.65(toml-rs/toml#730), we could cancel the version limit of toml and drop our MSRV to 1.65 too.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.76%. Comparing base (8ab1b34) to head (0254d52).
Report is 2 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #381      +/-   ##
==========================================
+ Coverage   63.39%   63.76%   +0.37%     
==========================================
  Files          24       25       +1     
  Lines        1557     1565       +8     
==========================================
+ Hits          987      998      +11     
+ Misses        570      567       -3     

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[bconn98]

I'm good with dropping the toml limitation. However, is there implicit benefit to dropping the MSRV? On a separate thread a few months back, there had been talk of ~1 year MSRV support.

[Dirreke]

IMO, the lower MSRV is, the more user can use log4rs. As we dont need the new feature in higher version of MSRV now, I believe dropping MSRV has benefits. I remember our policy is at least 1 year MSRV, so it's ok to downgrade MSRV.

However, if you don't want to downgrade it, I'm also good about that and I can edit this PR. Thanks!

[bconn98]

Good enough for me. The only "reason" I had to bump was once_cell is getting merged into std. But it's not new / needed functionality so not a priority.