Simplify push_pop_{max, min} and replace_{max, min} implementations

[calebsander]

• Use peek_{max, min}_mut() in push_pop_{max, min}() and replace_{max, min}() to reduce code duplication. Comparing the generated assembly, this seems to have a few performance effects (but I haven't benchmarked them):
  • push_pop_{max, min}() avoid swapping element to the heap if it is equal to max/min
  • push_pop_max() and replace_max() each avoid 2 bounds checks
  • push_pop_min() avoids a branch instruction
  • replace_{max, min}() avoid bubbling up the inserted value if the heap is empty
  • replace_max() swaps the min with element in a register instead of swapping two indices in the heap
  • The Peek{Max, Min}Mut struct is spilled to the stack
• Avoid sifting a Peek{Max, Min}Mut if it was never mutably dereferenced (copied from Rust's BinaryHeap: Avoid useless sift_down when std::collections::binary_heap::PeekMut is never mutably dereferenced rust-lang/rust#75974).
• Also fixes an overflow when dropping PeekMaxMut on a 1-element heap (which the quickcheck tests were now able to discover). Added a test for this.

[codecov-commenter]

Codecov Report

Merging #8 into master will decrease coverage by 0.15%.
The diff coverage is 94.28%.

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
- Coverage   98.70%   98.55%   -0.16%     
==========================================
  Files           3        3              
  Lines         541      552      +11     
==========================================
+ Hits          534      544      +10     
- Misses          7        8       +1     

Impacted Files	Coverage Δ
src/lib.rs	97.69% <94.28%> (-0.26%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9aba91a...25096db. Read the comment docs.

[tov]

Hey, just saw this! Sorry for being slow. I have very limited time right now, but from a cursory glance, it looks excellent!

[fbernier]

This PR, along with #11, look awesome. Great work @calebsander !

[codecov-io]

Codecov Report

Merging #8 (25096db) into master (9aba91a) will decrease coverage by 0.15%.
The diff coverage is 94.28%.

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
- Coverage   98.70%   98.55%   -0.16%     
==========================================
  Files           3        3              
  Lines         541      552      +11     
==========================================
+ Hits          534      544      +10     
- Misses          7        8       +1     

Impacted Files	Coverage Δ
src/lib.rs	97.69% <94.28%> (-0.26%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9aba91a...22a4561. Read the comment docs.

[codecov-commenter]

Codecov Report

Merging #8 (5f6dd4f) into master (9aba91a) will increase coverage by 0.44%.
The diff coverage is 100.00%.

❗ Current head 5f6dd4f differs from pull request most recent head 0ba722c. Consider uploading reports for the commit 0ba722c to get more accurate results

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
+ Coverage   98.70%   99.15%   +0.44%     
==========================================
  Files           3        3              
  Lines         541      589      +48     
==========================================
+ Hits          534      584      +50     
+ Misses          7        5       -2     

Impacted Files	Coverage Δ
src/lib.rs	98.82% <100.00%> (+0.87%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d287f92...0ba722c. Read the comment docs.