Reduce number of String allocations

[sunsided]

Implements a possible solution for #5. Builds upon #3 for the ToString support. The lazy evaluation allows to defer the to_string() call until the rendering actually takes place.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (a2c0a13) to head (2dd9df5).
Report is 23 commits behind head on main.

❗ Current head 2dd9df5 differs from pull request most recent head 70532fe

Please upload reports for the commit 70532fe to get more accurate results.

Additional details and impacted files

@@            Coverage Diff            @@
##              main        #6   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          132       207   +75     
=========================================
+ Hits           132       207   +75     

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[sunsided]

After adding indirection via QueryPart<'a>, performance degraded:

     Running benches/bench.rs (target/release/deps/bench-8bd30fe3b3e7b365)
with_value              time:   [416.94 ns 439.28 ns 463.03 ns]
                        change: [+11.309% +16.696% +22.573%] (p = 0.00 < 0.05)
                        Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
  6 (6.00%) high mild
  2 (2.00%) high severe

with_opt_value          time:   [943.02 ns 968.75 ns 994.36 ns]
                        change: [+7.9468% +12.170% +16.164%] (p = 0.00 < 0.05)
                        Performance has regressed.
Found 7 outliers among 100 measurements (7.00%)
  7 (7.00%) high mild

push_opt_and_append     time:   [654.08 ns 668.25 ns 685.17 ns]
                        change: [+38.901% +43.454% +48.391%] (p = 0.00 < 0.05)
                        Performance has regressed.
Found 7 outliers among 100 measurements (7.00%)
  4 (4.00%) high mild
  3 (3.00%) high severe