infra: release script, validate proper ICEBERG_VERSION variable

[kevinjqliu]

Which issue does this PR close?

• Closes #.

What changes are included in this PR?

Add a check that the input ICEBERG_VERSION variable is in the proper format, i.e. 0.8.0. Otherwise, the source directory and zip file will have the wrong name

Are these changes tested?

Added these 3 lines:

echo "Release version: $release_version"
echo "Git branch: $git_branch"
echo "Source directory: apache-iceberg-rust-$release_version"

This PR:

➜  iceberg-rust git:(kevinjqliu/validate-version) ✗ ICEBERG_VERSION=rc.1 ./scripts/release.sh  
var is set to 'rc.1'
Error: ICEBERG_VERSION (rc.1) must be in the format: <number>.<number>.<number>
➜  iceberg-rust git:(kevinjqliu/validate-version) ✗ ICEBERG_VERSION=0.8.0 ./scripts/release.sh 
var is set to '0.8.0'
Release version: 0.8.0
Git branch: release-0.8.0-rc.1
Source directory: apache-iceberg-rust-0.8.0

main:

➜  iceberg-rust git:(kevinjqliu/validate-version) ✗ ICEBERG_VERSION=rc.1 ./scripts/release.sh 
var is set to 'rc.1'
Release version: rc.1
Git branch: release-rc.1-rc.1
Source directory: apache-iceberg-rust-rc.1
➜  iceberg-rust git:(kevinjqliu/validate-version) ✗ ICEBERG_VERSION=0.8.0 ./scripts/release.sh
var is set to '0.8.0'
Release version: 0.8.0
Git branch: release-0.8.0-rc.1
Source directory: apache-iceberg-rust-0.8.0