Rename gravity_constant to gravity

[JoshuaLampert]

To stay consistent with the Trixi.jl ecosystem, cf. trixi-framework/Trixi.jl#2357 and to avoid any confusion.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.07%. Comparing base (1ed4b8c) to head (2cb5747).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #174   +/-   ##
=======================================
  Coverage   98.07%   98.07%           
=======================================
  Files          20       20           
  Lines        1920     1920           
=======================================
  Hits         1883     1883           
  Misses         37       37           

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[github-actions]

Benchmark Results

	main	2cb5747...	main/2cb574741aea57...
bbm_1d/bbm_1d_basic.jl	14.7 ± 0.65 μs	13.9 ± 0.36 μs	1.06
bbm_1d/bbm_1d_fourier.jl	0.527 ± 0.094 ms	0.527 ± 0.08 ms	1
bbm_bbm_1d/bbm_bbm_1d_basic_reflecting.jl	0.0805 ± 0.00042 ms	0.0806 ± 0.00046 ms	0.999
bbm_bbm_1d/bbm_bbm_1d_dg.jl	0.034 ± 0.00052 ms	0.0343 ± 0.00051 ms	0.992
bbm_bbm_1d/bbm_bbm_1d_relaxation.jl	27.3 ± 0.43 μs	27.6 ± 0.46 μs	0.989
bbm_bbm_1d/bbm_bbm_1d_upwind_relaxation.jl	0.0484 ± 0.00054 ms	0.0484 ± 0.00051 ms	1
hyperbolic_serre_green_naghdi_1d/hyperbolic_serre_green_naghdi_dingemans.jl	4.12 ± 0.014 μs	4.14 ± 0.013 μs	0.993
serre_green_naghdi_1d/serre_green_naghdi_well_balanced.jl	0.197 ± 0.007 ms	0.203 ± 0.0086 ms	0.969
svaerd_kalisch_1d/svaerd_kalisch_1d_dingemans_relaxation.jl	0.145 ± 0.0036 ms	0.147 ± 0.0035 ms	0.985
time_to_load	1.97 ± 0.0015 s	2.02 ± 0.047 s	0.976

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.

[ranocha]

Thanks!