Use unified caching when possible

[xiwenc]

fixes #103

[github-actions]

Merging this branch changes the coverage (2 decrease, 1 increase)

Impacted Packages	Coverage Δ	🤖
github.com/mxlint/mxlint-cli	0.00% (ø)
github.com/mxlint/mxlint-cli/lint	71.85% (-0.17%)	👎
github.com/mxlint/mxlint-cli/mpr	77.42% (+0.29%)	👍
github.com/mxlint/mxlint-cli/serve	20.54% (-1.37%)	👎

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Coverage by file

Changed files (no unit tests)

Changed File	Coverage Δ	Total	Covered	Missed	🤖
github.com/mxlint/mxlint-cli/lint/cache.go	68.42% (-1.69%)	95 (+8)	65 (+4)	30 (+4)	👎
github.com/mxlint/mxlint-cli/lint/config.go	86.05% (-0.42%)	172 (+2)	148 (+1)	24 (+1)	👎
github.com/mxlint/mxlint-cli/main.go	0.00% (ø)	175 (+33)	0	175 (+33)
github.com/mxlint/mxlint-cli/mpr/mpr.go	80.36% (+0.07%)	504 (+88)	405 (+71)	99 (+17)	👍
github.com/mxlint/mxlint-cli/mpr/mx_units_v2.go	52.43% (+1.43%)	103 (+3)	54 (+3)	49	👍
github.com/mxlint/mxlint-cli/mpr/types.go	0.00% (ø)	0	0	0
github.com/mxlint/mxlint-cli/serve/serve.go	9.04% (-0.73%)	188 (+14)	17	171 (+14)	👎

Please note that the "Total", "Covered", and "Missed" counts above refer to code statements instead of lines of code. The value in brackets refers to the test coverage of that file in the old version of the code.

Changed unit test files

• github.com/mxlint/mxlint-cli/mpr/mpr_test.go