build!: bump rust to 1.76 and add rust update script

[lklimek]

Issue being fixed or feature implemented

New Rust was released

What was done?

• bumped version to 1.76 in github actions, rust-toolchain.toml, Dockerfile, Cargo.toml files and README.md
• added script that makes such updates easy

How Has This Been Tested?

Run script locally + Github Actions

Breaking Changes

New Rust version 1.76 is required

Checklist:

• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have added or updated relevant unit/integration/functional/e2e tests
• [x] I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• [x] I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• [ ] I have assigned this pull request to a milestone