add parameter for initiating bgrewriteaof on exceeding maximum AOF size

[kronwerk]

there are some scenarios of filling up the whole disk besides any chosen AOF rewrite strategy - the simplest is this:

• we have auto-aof-rewrite-percentage 100,
• and last automatic rewrite compacted AOF to 51% of disk,
  -> we'll never try again.

we can lower auto-percentage, but in some cases it's not what we want to. I suggest that we add soft upper limit in this PR:

• if no AOF rewrite is running currently,
• and limit is set in config,
• and AOF exceed the limit,
• and last rewrite compacted AOF to somewhat smaller than limit (otherwise we might end up with useless attempts of uninterrupted rewrites)
  -> bgrewriteaof is initiated.

this doesn't completely solves the problem, but gives some additional possibilities for some users to improve the situation initially described in #540 (noticed that solution from the issue seems to be inappropriate for some cases)

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 71.36%. Comparing base (663dac9) to head (6bff01a).

Files with missing lines	Patch %	Lines
src/aof.c	70.00%	3 Missing ⚠️
src/server.c	90.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #2368      +/-   ##
============================================
+ Coverage     71.30%   71.36%   +0.06%     
============================================
  Files           123      123              
  Lines         67122    67135      +13     
============================================
+ Hits          47859    47912      +53     
+ Misses        19263    19223      -40     

Files with missing lines	Coverage Δ
src/config.c	78.47% <ø> (ø)
src/server.h	100.00% <ø> (ø)
src/server.c	88.09% <90.00%> (-0.01%)	⬇️
src/aof.c	80.38% <70.00%> (-0.15%)	⬇️

... and 10 files with indirect coverage changes

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[kronwerk]

@valkey-io/core-team PTAL