Make ext-bcmath available by default for all php versions

[Xerkus]

ext-bcmath is required by tools. apt install -y php-bcmath installs php8.3-bcmath which is not a default php version. Composer install for tools consequently fails. See #212

I think it would be appropriate to install the extension for all php versions rather than just the single version that happens to be used by tools.

[boesing]

Afaik its only necessary for the bc Tool. that - on the other hand - is only executed on the container default php Version. So we just have to ensure it is available for the default version. for all other projects requiring the extension, the matrix is already pushing the requirement via job JSON which then installs the extension(s) on demand.

Yes, we can install and enable the extension for all PHP versions but its not a must-have.

Using php-bcmath was good enough until php 8.3 came out. using explicit php version for installing the default extension would be a fix for the referenced issue in OP.

[Xerkus]

It's not really about extensions that could be installed where needed. Ideally we would want to reduce any unnecessary differences between versions used in CI tasks. That is the reason I went with this approach instead of just changing to specific version for the tool installation.