Extend all analytic functions in base for octonions

[sethaxen]

This PR is the companion of JuliaGeometry/Quaternions.jl#56. Like that PR for quaternions, it draws on a more general result that allows us to extend all complex analytic functions in Base to the octonions with a function extend_analytic.

Since extend_analytic is faster than the current implementations of sqrt and exp, those are refactored to use it. The PR also speeds up log and, for clarity, refactors it to adopt the same notation as extend_analytic.

Here's a performance comparison:

julia> using Octonions, BenchmarkTools

julia> o = randn(OctonionF64);

Before:

julia> @btime exp($o);
  54.570 ns (0 allocations: 0 bytes)

julia> @btime sqrt($o);
  184.861 ns (0 allocations: 0 bytes)

julia> @btime log($o);
  99.939 ns (0 allocations: 0 bytes)

After:

julia> @btime exp($o);
  42.833 ns (0 allocations: 0 bytes)

julia> @btime sqrt($o);
  38.143 ns (0 allocations: 0 bytes)

julia> @btime log($o);
  67.569 ns (0 allocations: 0 bytes)

[codecov]

Codecov Report

Merging #16 (8c0525c) into main (2bc326b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #16   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            2         2           
  Lines           92       101    +9     
=========================================
+ Hits            92       101    +9     

Impacted Files	Coverage Δ
src/octonion.jl	100.00% <100.00%> (ø)

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[hyrodium]

LGTM!