Remove unnecessary unaliasing allocation

[LilithHafner]

Profiling reveals that this append! call allocates. Benchmarking reveals that changing the implementation speeds things up. Hopefully future versions of Julia will be clever enough to determine that there is no aliasing in the append! case but on Julia 1.10.5 append! makes a copy to prevent possible aliasing.

PR	In Memory
		incompressible	huffman	runlength	graph
small	deflate	2.0	2.9	4.0	2.4
	zlib	2.7	2.9	3.9	2.5
	gzip	3.9	3.0	3.4	2.6
medium	deflate	1.5	3.3	2.6	3.1
	zlib	3.6	3.5	2.8	3.2
	gzip	5.0	3.5	3.5	3.4
large	deflate	3.5	3.5	2.6	3.3
	zlib	4.1	3.5	2.8	3.3
	gzip	5.2	3.6	3.2	3.6

master	In Memory
		incompressible	huffman	runlength	graph
small	deflate	2.1	3.4	3.9	3.5
	zlib	2.8	3.5	3.9	3.6
	gzip	4.2	3.6	3.5	3.5
medium	deflate	1.6	4.4	3.8	5.1
	zlib	3.5	4.5	4.0	4.8
	gzip	4.9	4.9	3.9	4.8
large	deflate	3.5	4.7	3.8	7.0
	zlib	4.0	4.6	3.8	5.1
	gzip	5.4	4.7	4.3	5.2

This is a big improvement for the large deflate graph case!

julia> @b compressed inflate
129.791 ms (1605215 allocs: 118.158 MiB, 2.13% gc time)

shell> git checkout lh/perf-alloc-1
Previous HEAD position was cc77be7 Fix correctness for 32-bit Julia.
Switched to branch 'lh/perf-alloc-1'
Your branch is up to date with 'origin/lh/perf-alloc-1'.

julia> @b compressed inflate
81.500 ms (8300 allocs: 20.690 MiB)

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.36%. Comparing base (f16eec8) to head (4e4f400).
Report is 4 commits behind head on master.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #24   +/-   ##
=======================================
  Coverage   99.35%   99.36%           
=======================================
  Files           1        1           
  Lines         468      470    +2     
=======================================
+ Hits          465      467    +2     
  Misses          3        3           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[GunnarFarneback]

Looks good. Notice that this was one of the optimizations identified in #9, but either this implementation is better or it has become more effective since then.