* ci: Update linter to 1.59.1.
Also remove deprecated linter "vetshadow", its functionality is now
included in the "govet" linter.
* ci: Add new linters.
- fatcontext - Detects nested contexts in loops.
- mirror - Reports wrong mirror patterns of bytes/strings usage.
- nilnil - Checks that there is no simultaneous return of nil error and
an invalid value.
- usestdlibvars - detect the possibility to use variables/constants from
the Go standard library.
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