fix: cache credential resolution with the AWS credential provider

[rtyler]

object_store invokes get_credential on every invocation of a get/list/put/etc. The provider invocation for environment based credentials is practically zero-cost, so this has no/low overhead.

In the case of the AssumeRoleProvider or any provider which has some cost, such as an invocation of the AWS STS APIs, this can result in rate-limiting or service quota exhaustion.

In order to prevent this, the credentials are attempted to be cached only so long as they have no expired, which is defined in the aws_credential_types::Credential struct

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 84.14634% with 13 lines in your changes missing coverage. Please review.

Project coverage is 72.33%. Comparing base (b4eff70) to head (3a25235). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/aws/src/credentials.rs	84.14%	0 Missing and 13 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2987 +/- ## ========================================== + Coverage 72.27% 72.33% +0.06% ========================================== Files 128 128 Lines 40341 40420 +79 Branches 40341 40420 +79 ========================================== + Hits 29155 29237 +82 + Misses 9335 9305 -30 - Partials 1851 1878 +27 ```

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