Add build profile optimized for binary size

[apiraino]

This patch adds a new build profile optimized for binary size.

If we exclude the triagebot application, when building the other binaries under ./src/bin I think it can make sense to optimize for binary size rathen than performance. When taken to the extreme (as in this patch), the differenze is just huge, see the following table (rust nightly 1.77):

$ la -h target/{release,opt-size}/{compiler,types,lang,prioritization-agenda}
-rwxr-xr-x 2 me me 4.0M Jan 24 17:13 target/opt-size/compiler
-rwxr-xr-x 2 me me 4.1M Jan 24 17:13 target/opt-size/lang
-rwxr-xr-x 2 me me 4.1M Jan 24 17:13 target/opt-size/prioritization-agenda
-rwxr-xr-x 2 me me 4.0M Jan 24 17:13 target/opt-size/types
-rwxr-xr-x 2 me me 140M Jan 24 17:21 target/release/compiler
-rwxr-xr-x 2 me me 141M Jan 24 17:21 target/release/lang
-rwxr-xr-x 2 me me 141M Jan 24 17:21 target/release/prioritization-agenda
-rwxr-xr-x 2 me me 140M Jan 24 17:21 target/release/types

I like to run the build of these ancillary tools with cargo build --bins --profile=opt-size.

Opinions?

Thanks for a review.