fix(oob): support legacy prefix in attachments

[TimoGlastra]

Fix issue of the oob module not being able to handle the legacy did sov prefix on attachment in oob invitations.

Issue as reported on discord:

AFJ is throwing an error when i accept an oob invitation with a present-proof/credential-offer attachment from acapy, Error msg: There is no message in requests~attach supported by agent. It's due to LegacyDidSovPrefix in the message type. It fails at this step : https://github.com/hyperledger/aries-framework-javascript/blob/main/packages/core/src/modules/oob/OutOfBandModule.ts#L599

[codecov-commenter]

Codecov Report

Merging #931 (ffe91c8) into main (9e30bb2) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #931   +/-   ##
=======================================
  Coverage   87.73%   87.74%           
=======================================
  Files         475      475           
  Lines       11349    11354    +5     
  Branches     1875     1879    +4     
=======================================
+ Hits         9957     9962    +5     
  Misses       1325     1325           
  Partials       67       67           

Impacted Files	Coverage Δ
packages/core/src/modules/oob/OutOfBandModule.ts	87.59% <100.00%> (+0.09%)	⬆️
packages/core/src/utils/messageType.ts	97.82% <100.00%> (+0.15%)	⬆️

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[morrieinmaas]

lgtm!