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ARROW-5809: [CI] [Rust] Travis runs dockerized Rust build

The specific nightly version of Rust is installed when building the Docker image, so it no longer needs to be downloaded on every run.

I have removed tarpaulin (code coverage) for now since it has been failing for many months anyway and there are challenges to getting it working with docker-compose. I will create a separate story for this.

Closes #5586 from andygrove/ARROW-5809 and squashes the following commits:

6fe353563 <Sutou Kouhei> Fix lint errors
6bc83e2e7 <Sutou Kouhei> Use buster
1fbf1da5a <Sutou Kouhei> Use $(...)
0bfc0dfa6 <Sutou Kouhei> Remove needless empty line
55b6bc950 <Andy Grove> docker-compose build works locally
b8edb1075 <Andy Grove> Save
4c872b101 <Andy Grove> remove travis scripts
f638f2988 <Andy Grove> save progress
72c1d900a <Andy Grove> Set default toolchain, remove tarpaulin
2bc0c507a <Andy Grove> pre-install correct version of Rust
adc4d7804 <Andy Grove> Travis runs dockerized Rust build

Lead-authored-by: Andy Grove <andygrove73@gmail.com>
Co-authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Andy Grove <andygrove73@gmail.com>