.Net: DotNet: Remove cosmosdb memory store (microsoft#2239)

### Motivation and Context
CosmosDB memory store is an extremely inefficient and expensive to store
vectors in cloud storage.

If a user wishes to use Azure to host a vector indexing service,
existing SK Memory alternatives that we recommend are:
- Azure Cognitive Search
- Postgres Memory Store - pg vector can be enabled for Azure Database
for PostgreSQL
https://learn.microsoft.com/en-us/azure/postgresql/flexible-server/how-to-use-pgvector
### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->

Removes CosmosMemoryStore from SK repo. 

<!-- Before submitting this PR, please make sure: -->

- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

---------

Co-authored-by: Gil LaHaye <gillahaye@microsoft.com>

dotnet/SK-dotnet.sln

@@ -61,8 +61,6 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Connectors.Memory.Qdrant",
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Connectors.Memory.Sqlite", "src\Connectors\Connectors.Memory.Sqlite\Connectors.Memory.Sqlite.csproj", "{EC004F12-2F60-4EDD-B3CD-3A504900D929}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Connectors.Memory.CosmosDB", "src\Connectors\Connectors.Memory.CosmosDB\Connectors.Memory.CosmosDB.csproj", "{EA61C289-7928-4B78-A9C1-7AAD61F907CD}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Connectors.Memory.Postgres", "src\Connectors\Connectors.Memory.Postgres\Connectors.Memory.Postgres.csproj", "{C9F957FA-A70F-4A6D-8F95-23FCD7F4FB87}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Connectors.Memory.Redis", "src\Connectors\Connectors.Memory.Redis\Connectors.Memory.Redis.csproj", "{3720F5ED-FB4D-485E-8A93-CDE60DEF0805}"
@@ -240,11 +238,6 @@ Global
 		{EC004F12-2F60-4EDD-B3CD-3A504900D929}.Publish|Any CPU.Build.0 = Publish|Any CPU
 		{EC004F12-2F60-4EDD-B3CD-3A504900D929}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{EC004F12-2F60-4EDD-B3CD-3A504900D929}.Release|Any CPU.Build.0 = Release|Any CPU
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD}.Publish|Any CPU.ActiveCfg = Release|Any CPU
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD}.Release|Any CPU.Build.0 = Release|Any CPU
 		{C9F957FA-A70F-4A6D-8F95-23FCD7F4FB87}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{C9F957FA-A70F-4A6D-8F95-23FCD7F4FB87}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{C9F957FA-A70F-4A6D-8F95-23FCD7F4FB87}.Publish|Any CPU.ActiveCfg = Publish|Any CPU
@@ -390,7 +383,6 @@ Global
 		{EB3FC57F-E591-4C88-BCD5-B6A1BC635168} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{5DEBAA62-F117-496A-8778-FED3604B70E2} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{EC004F12-2F60-4EDD-B3CD-3A504900D929} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
-		{EA61C289-7928-4B78-A9C1-7AAD61F907CD} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{C9F957FA-A70F-4A6D-8F95-23FCD7F4FB87} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{3720F5ED-FB4D-485E-8A93-CDE60DEF0805} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{185E0CE8-C2DA-4E4C-A491-E8EB40316315} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
@@ -415,12 +407,12 @@ Global
 		{B00AD427-0047-4850-BEF9-BA8237EA9D8B} = {958AD708-F048-4FAF-94ED-D2F2B92748B9}
 		{DB950192-30F1-48B1-88D7-F43FECCA1A1C} = {958AD708-F048-4FAF-94ED-D2F2B92748B9}
 		{1C19D805-3573-4477-BF07-40180FCDE1BD} = {958AD708-F048-4FAF-94ED-D2F2B92748B9}
+		{3CDE10B2-AE8F-4FC4-8D55-92D4AD32E144} = {958AD708-F048-4FAF-94ED-D2F2B92748B9}
 		{0D0C4DAD-E6BC-4504-AE3A-EEA4E35920C1} = {9ECD1AA0-75B3-4E25-B0B5-9F0945B64974}
 		{E6EDAB8F-3406-4DBF-9AAB-DF40DC2CA0FA} = {FA3720F1-C99A-49B2-9577-A940257098BF}
 		{677F1381-7830-4115-9C1A-58B282629DC6} = {0247C2C9-86C3-45BA-8873-28B0948EDC0C}
 		{4762BCAF-E1C5-4714-B88D-E50FA333C50E} = {078F96B4-09E1-4E0E-B214-F71A4F4BF633}
 		{C754950A-E16C-4F96-9CC7-9328E361B5AF} = {FA3720F1-C99A-49B2-9577-A940257098BF}
-		{3CDE10B2-AE8F-4FC4-8D55-92D4AD32E144} = {958AD708-F048-4FAF-94ED-D2F2B92748B9}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {FBDC56A3-86AD-4323-AA0F-201E59123B83}