New deserialization API - preparations

[wprzytula]

This PR consists the first bunch of minor preparatory steps for the main leap of the deserialization refactor, extracted from #1057 as @Lorak-mmk requested.

For explanation and broader context see #1057.
Ref: #462

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• [ ] I added relevant tests for new features and bug fixes.
• All commits compile, pass static checks and pass test.
• PR description sums up the changes and reasons why they should be introduced.
• I have provided docstrings for the public items that I want to introduce.
• [ ] I have adjusted the documentation in ./docs/source/.
• [ ] I added appropriate Fixes: annotations to PR description.

[github-actions]

cargo semver-checks detected some API incompatibilities in this PR.
Checked commit: d47aa81

See the following report for details:

cargo semver-checks output

./scripts/semver-checks.sh --baseline-rev 5752af488655287fc332ec3dd68645ef522e0d7c
+ cargo semver-checks -p scylla -p scylla-cql --baseline-rev 5752af488655287fc332ec3dd68645ef522e0d7c
     Cloning 5752af488655287fc332ec3dd68645ef522e0d7c
     Parsing scylla v0.13.0 (current)
      Parsed [  22.765s] (current)
     Parsing scylla v0.13.0 (baseline)
      Parsed [  20.042s] (baseline)
    Checking scylla v0.13.0 -> v0.13.0 (no change)
     Checked [   0.079s] 79 checks: 78 pass, 1 fail, 0 warn, 0 skip

--- failure struct_pub_field_missing: pub struct's pub field removed or renamed ---

Description:
A publicly-visible struct has at least one public field that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.34.0/src/lints/struct_pub_field_missing.ron

Failed in:
  field col_specs of struct QueryResult, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-5752af488655287fc332ec3dd68645ef522e0d7c/e5083df900adadf2ab85ec0d0ea2d0b0e87030b8/scylla/src/transport/query_result.rs:22
  field col_specs of struct QueryResult, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-5752af488655287fc332ec3dd68645ef522e0d7c/e5083df900adadf2ab85ec0d0ea2d0b0e87030b8/scylla/src/transport/query_result.rs:22

     Summary semver requires new major version: 1 major and 0 minor checks failed
    Finished [  42.933s] scylla
     Parsing scylla-cql v0.2.0 (current)
      Parsed [  10.073s] (current)
     Parsing scylla-cql v0.2.0 (baseline)
      Parsed [  10.049s] (baseline)
    Checking scylla-cql v0.2.0 -> v0.2.0 (no change)
     Checked [   0.084s] 79 checks: 76 pass, 3 fail, 0 warn, 0 skip

--- failure constructible_struct_adds_field: externally-constructible struct adds field ---

Description:
A pub struct constructible with a struct literal has a new pub field. Existing struct literals must be updated to include the new field.
        ref: https://doc.rust-lang.org/reference/expressions/struct-expr.html
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.34.0/src/lints/constructible_struct_adds_field.ron

Failed in:
  field Rows.paging_state_response in /home/runner/work/scylla-rust-driver/scylla-rust-driver/scylla-cql/src/frame/response/result.rs:490

--- failure enum_variant_added: enum variant added on exhaustive enum ---

Description:
A publicly-visible enum without #[non_exhaustive] has a new variant.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#enum-variant-new
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.34.0/src/lints/enum_variant_added.ron

Failed in:
  variant ParseError:DeserializationTypeCheckError in /home/runner/work/scylla-rust-driver/scylla-rust-driver/scylla-cql/src/frame/frame_errors.rs:49

--- failure struct_pub_field_missing: pub struct's pub field removed or renamed ---

Description:
A publicly-visible struct has at least one public field that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.34.0/src/lints/struct_pub_field_missing.ron

Failed in:
  field paging_state of struct ResultMetadata, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-5752af488655287fc332ec3dd68645ef522e0d7c/e5083df900adadf2ab85ec0d0ea2d0b0e87030b8/scylla-cql/src/frame/response/result.rs:434

     Summary semver requires new major version: 3 major and 0 minor checks failed
    Finished [  20.256s] scylla-cql
make: *** [Makefile:61: semver-rev] Error 1

[muzarski]

Here as well (regarding @Lorak-mmk 's comment). I think this should belong to other commit. I am not even sure why we were modifying received rows (by moving the paging state out of them), even though we send them via some channel later.

[wprzytula]

We can do that because the iterator manages paging state itself, and it does not expose any getters of it.

[wprzytula]

v1.1: reverted paging_state.clone() to paging_state.take() in iterator.

[wprzytula]

v1.1.1: fixed tests in QueryResult.

[wprzytula]

v1.2: rebased on main.

[wprzytula]

v1.2.1: fixed compile error on MSRV due to:
error[E0277]: the trait bound `[u8]: Default` is not satisfied