Replace ensureAttributesCapacity with slices.Grow

[pellared]

Replace ensureAttributesCapacity with slices.Grow once we drop support for Go 1.20.

How about inlining the slices.Grow implementation instead of referencing golang.org/x/exp?

Originally posted by @pellared in https://github.com/open-telemetry/opentelemetry-go/pull/4818#discussion_r1446458963

[lizthegrey]

You also will, while you're in the same code, also want to change the if x > y { foo(x) } else { foo(y) } added in #4818 to a min() per go1.21.

[sumit1606]

@pellared Mind if I take a stab at it ?

[lizthegrey]

@pellared Mind if I take a stab at it ?

go1.22 is not yet out, so go1.20 is still supported. Feel free to prepare, but do not land, a PR that does the cleanup I suggested.