refactor(esplora): clear remaining panic paths

[reez]

Description

This PR clears remaining panic paths from bdk_esplora, replacing them with proper error handling.

Attempting to address https://github.com/bitcoindevkit/bdk_wallet/issues/30 for Esplora

Notes to the reviewers

Open to any and all feedback on this.

Other PR's made along these lines:

• https://github.com/bitcoindevkit/bdk/pull/1981 (electrum)
• https://github.com/bitcoindevkit/bdk/pull/1971 (esplora)

Changelog notice

• Clear remaining panic paths from bdk_esplora.rs.

Checklists

All Submissions:

• [x] I followed the contribution guidelines

New Features:

• [ ] I've added tests for the new feature
• [ ] I've added docs for the new feature

Bugfixes:

• [ ] This pull request breaks the existing API
• [ ] I've added tests to reproduce the issue which are now passing
• [ ] I'm linking the issue being fixed by this PR