Add report allocs function

[charleskawczynski]

This PR:

• Adds a Requires dependency
• Adds a new function, report_allocs, which tabulates allocations per line, using PrettyTables, if it's been loaded

This function was ported over from ReportMetrics.jl.

Here is an example usage, which was also added to the docs / readme:

julia> import Coverage
julia> import PrettyTables # load report_allocs
julia> mktempdir() do path
           open(joinpath(path, "example.jl"), "w") do io
               println(io, "for i in 1:1000")
               println(io, "    x = []")
               println(io, "    push!(x, 1)")
               println(io, "    push!(x, [1,2,3,4])")
               println(io, "    push!(x, \"stringy-string\")")
               println(io, "end")
           end
           Coverage.report_allocs(;
               run_cmd=`$(Base.julia_cmd()) --track-allocation=all $(joinpath(path, "example.jl"))`,
               dirs_to_monitor = [path],
               process_filename = fn -> replace(fn, path=>""),
           )
       end
3 unique allocating sites, 224000 total bytes
┌──────────────────────┬─────────────┬───────────────┐
│ <file>:<line number> │ Allocations │ Allocations % │
│                      │   (bytes)   │    (xᵢ/∑x)    │
├──────────────────────┼─────────────┼───────────────┤
│ example.jl:4         │    96000    │      43       │
│ example.jl:3         │    80000    │      36       │
│ example.jl:2         │    48000    │      21       │
└──────────────────────┴─────────────┴───────────────┘

[coveralls]

Pull Request Test Coverage Report for Build 3991864528

• 62 of 82 (75.61%) changed or added relevant lines in 2 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-3.7%) to 87.013%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/report_allocs.jl	59	79	74.68%
<!--	Total:	62	82	75.61%	-->

Files with Coverage Reduction	New Missed Lines	%
src/codecovio.jl	2	87.39%
src/coveralls.jl	2	94.74%
<!--	Total:	4		-->

Totals
Change from base Build 3679300279:	-3.7%
Covered Lines:	268
Relevant Lines:	308

---

💛 - Coveralls

[codecov[bot]]

Codecov Report

Merging #337 (0daf25a) into master (453ba9f) will decrease coverage by 3.33%. The diff coverage is 76.82%.

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
- Coverage   90.66%   87.33%   -3.33%     
==========================================
  Files           2        4       +2     
  Lines         225      308      +83     
==========================================
+ Hits          204      269      +65     
- Misses         21       39      +18     

Impacted Files	Coverage Δ
src/report_allocs.jl	75.94% <75.94%> (ø)
src/Coverage.jl	100.00% <100.00%> (ø)
src/coveralls.jl	94.73% <0.00%> (-1.76%)	:arrow_down:
src/codecovio.jl	87.38% <0.00%> (+2.70%)	:arrow_up:

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[charleskawczynski]

Bump!

[charleskawczynski]

Bump!

[charleskawczynski]

Closing in light of https://github.com/JuliaLang/julia/pull/48070.